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103-446: SWIR may refer to: Short-wavelength infrared , a region of the infrared light spectrum Sierra Wireless , a multinational communication company Southwest Indian Ridge , a mid-ocean ridge between Africa and Antarctica See also [ edit ] Svir (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

206-471: A passive missile guidance system , which uses the emission from a target of electromagnetic radiation in the infrared part of the spectrum to track it. Missiles that use infrared seeking are often referred to as "heat-seekers" since infrared (IR) is just below the visible spectrum of light in frequency and is radiated strongly by hot bodies. Many objects such as people, vehicle engines, and aircraft generate and retain heat, and as such, are especially visible in

309-524: A thermographic camera , with the fundamental difference that each pixel contains a full LWIR spectrum. Consequently, chemical identification of the object can be performed without a need for an external light source such as the Sun or the Moon. Such cameras are typically applied for geological measurements, outdoor surveillance and UAV applications. In infrared photography , infrared filters are used to capture

412-600: A chemical and electrical process and then converted back into visible light. Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source. The use of infrared light and night vision devices should not be confused with thermal imaging , which creates images based on differences in surface temperature by detecting infrared radiation ( heat ) that emanates from objects and their surrounding environment. Infrared radiation can be used to remotely determine

515-482: A continuous sequence of weather to be studied. These infrared pictures can depict ocean eddies or vortices and map currents such as the Gulf Stream, which are valuable to the shipping industry. Fishermen and farmers are interested in knowing land and water temperatures to protect their crops against frost or increase their catch from the sea. Even El Niño phenomena can be spotted. Using color-digitized techniques,

618-403: A convenient way to verify a successful imbibition is to put them in water until they sink, which takes about six hours when submerged in an infuser , and about 12 hours when they are floating on water. Seeds that keep floating need scarification in order to absorb water. The seedling stage begins when the seed coat splits open and exposes the root and cotyledons. It lasts from 1 to 4 weeks, and

721-490: A dark period, as plants undergo late day decline and therefore lighting during the late night hours is less effective. The amount of time to grow a cannabis plant indoors in the vegetative stage depends on the size of the flower, the light used, the size of the space, and how many plants are intended to flower at once, and how big the strain gets in "the stretch" (i.e., the first two weeks of flowering). Cannabis cultivators employ fertilizers high in nitrogen and potassium during

824-592: A day. In the Northern Hemisphere, growers typically plant seeds in mid-April, late May, or early June to provide plants a full four to nine months of growth. Harvest is usually between mid-September and early October. In North America, northern locations are preferred ( North Coast of California and British Columbia being particularly notable), but southern locations (such as Maui, Hawaii ) are also known to be good producers. Regulations permitting outdoor cultivation of cannabis vary from state to state in

927-462: A growth medium, the soil should be allowed to dry down adequately before re-watering. Humidity is an important part of plant growth. Dry conditions slow the rate of photosynthesis. Ideal levels of humidity for optimal growth are 40–60% RH. Nutrients are taken up from the soil by roots. Nutrient soil amendments ( fertilizers ) are added when the soil nutrients are depleted. Fertilizers can be chemical or organic, liquid or powder, and usually contain

1030-417: A method is prone to theft – so much so that some ingenious growers even attach pots to trees to decrease this possibility. Guerrilla growing has given birth to the activist movement Operation Overgrow , where the plant is grown with the explicit purpose of introducing the cannabis plant into the natural ecosystem. For outdoor cultivation, growers choose areas that receive twelve hours or more of sunlight

1133-456: A mixture of ingredients. Commercial fertilizers indicate the levels of NPK (nitrogen, phosphorus, and potassium). In general, cannabis needs more N than P and K during all life phases. The presence of secondary nutrients ( calcium , magnesium , sulfur ) is recommended. Micronutrients (e.g. iron, boron , chlorine , manganese , copper, zinc, molybdenum ) rarely manifest as deficiencies. Because cannabis' nutrient needs vary widely depending on

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1236-403: A molecule vibrates at a frequency characteristic of that bond. A group of atoms in a molecule (e.g., CH 2 ) may have multiple modes of oscillation caused by the stretching and bending motions of the group as a whole. If an oscillation leads to a change in dipole in the molecule then it will absorb a photon that has the same frequency. The vibrational frequencies of most molecules correspond to

1339-431: A more emissive one. For that reason, incorrect selection of emissivity and not accounting for environmental temperatures will give inaccurate results when using infrared cameras and pyrometers. Infrared is used in night vision equipment when there is insufficient visible light to see. Night vision devices operate through a process involving the conversion of ambient light photons into electrons that are then amplified by

1442-463: A near-IR laser may thus appear dim red and can present a hazard since it may actually be quite bright. Even IR at wavelengths up to 1,050 nm from pulsed lasers can be seen by humans under certain conditions. A commonly used subdivision scheme is: NIR and SWIR together is sometimes called "reflected infrared", whereas MWIR and LWIR is sometimes referred to as "thermal infrared". The International Commission on Illumination (CIE) recommended

1545-463: A significant amount of energy. For optimal health, cannabis plants require a period of light and a period of dark. It has been suggested that, when subjected to a regimen of constant light without a dark period, cannabis begins to show signs of decreased photosynthetic response, lack of vigor, and an overall decrease in vascular development. Typically, flowering is induced by providing at least 12 hours per day of complete darkness. Flowering in cannabis

1648-453: A soil-like medium under artificial light, adding plants are given water. Cultivating cannabis indoors is more complicated and expensive than growing outdoors, but it allows the cultivator complete control over the growing environment. Plants of any type can be grown faster indoors than out due to 24-hour light, additional atmospheric CO 2 , and controlled humidity which allows freer CO 2 respiration. Plants can also be grown indoors through

1751-503: A specific nanometer range, allowing for total control over the spectrum of the light. LEDs are able to produce all of their light in the photosynthetically active range (PAR) of the spectrum. Reflectors are often used in the lamps to maximize light efficiency. At a medium growing density of 15 plants and 430 watts per square meter, electricity costs are not insignificant. Plants or lights are moved as close together as possible so that they receive equal lighting and that all light coming from

1854-474: A specific range, typically with deviations no larger than 10 °C (18 °F) with a cooler night and warmer day. Adequate levels of CO 2 must be maintained for the plants to grow efficiently. It is also important to promote vigorous air circulation within the grow room, which is usually accomplished by mounting an extraction fan and one or more oscillating fans. Power supplies that can be unscrewed from lamp luminaires can be placed outside grow tents to reduce

1957-427: A spectrum of wavelengths, but sometimes only a limited region of the spectrum is of interest because sensors usually collect radiation only within a specific bandwidth. Thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wien's displacement law . The infrared band is often subdivided into smaller sections, although how

2060-405: A worldwide scale, this cooling method has been proposed as a way to slow and even reverse global warming , with some estimates proposing a global surface area coverage of 1-2% to balance global heat fluxes. IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants . These devices usually conform to standards published by IrDA ,

2163-411: Is a property of a surface that describes how its thermal emissions deviate from the ideal of a black body . To further explain, two objects at the same physical temperature may not show the same infrared image if they have differing emissivity. For example, for any pre-set emissivity value, objects with higher emissivity will appear hotter, and those with a lower emissivity will appear cooler (assuming, as

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2266-451: Is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Objects at room temperature will emit radiation concentrated mostly in the 8 to 25 μm band, but this is not distinct from the emission of visible light by incandescent objects and ultraviolet by even hotter objects (see black body and Wien's displacement law ). Heat

2369-426: Is also a technique called ' T-ray ' imaging, which is imaging using far-infrared or terahertz radiation . Lack of bright sources can make terahertz photography more challenging than most other infrared imaging techniques. Recently T-ray imaging has been of considerable interest due to a number of new developments such as terahertz time-domain spectroscopy . Infrared tracking, also known as infrared homing, refers to

2472-430: Is associated with spectra far above the infrared, extending into visible, ultraviolet, and even X-ray regions (e.g. the solar corona ). Thus, the popular association of infrared radiation with thermal radiation is only a coincidence based on typical (comparatively low) temperatures often found near the surface of planet Earth. The concept of emissivity is important in understanding the infrared emissions of objects. This

2575-537: Is being researched as an aid for visually impaired people through the Remote infrared audible signage project. Transmitting IR data from one device to another is sometimes referred to as beaming . IR is sometimes used for assistive audio as an alternative to an audio induction loop . Infrared vibrational spectroscopy (see also near-infrared spectroscopy ) is a technique that can be used to identify molecules by analysis of their constituent bonds. Each chemical bond in

2678-485: Is classified as part of optical astronomy . To form an image, the components of an infrared telescope need to be carefully shielded from heat sources, and the detectors are chilled using liquid helium . The sensitivity of Earth-based infrared telescopes is significantly limited by water vapor in the atmosphere, which absorbs a portion of the infrared radiation arriving from space outside of selected atmospheric windows . This limitation can be partially alleviated by placing

2781-503: Is clearly revealed in the first phase, the actual flowering. Males produce little ball-like flowers clustered together like grapes called panicles . Most plants (except auto flowering strains that flower independently of photoperiod ) begin to flower under diminishing light. In nature, cannabis plants sense the forthcoming winter as the Earth revolves about the Sun and daylight reduces in duration (see also season ). The next phase consists in

2884-488: Is common in both rural and urban areas. Outdoor cultivators tend to grow indica-based strains because of its heavy yields, quick maturing time, and short stature. Some growers prefer sativa because of its clear-headed ( cerebral ) high , better response to sunlight, and lower odor emissions. Growers cultivate on their own property or practice guerrilla farming i.e. to plant cannabis in remote areas such as forest clearings or mountain cliffs which they rarely visit. However, such

2987-522: Is consumed by the production of seeds, which can be half the mass of a fertilized bract; thus, to maximize resin by weight, infertile cultivation is preferred. Inflorescence that produce no seeds are called sin semilla (which translates to "without seeds" in Spanish, and is often misspelled as one word). Potent sin semilla is especially important to medical users, to minimize the amount of cannabis they must consume to be afforded relief. Cannabis with seeds

3090-423: Is counted as part of the microwave band, not infrared, moving the band edge of infrared to 0.1 mm (3 THz). Sunlight , at an effective temperature of 5,780  K (5,510 °C, 9,940 °F), is composed of near-thermal-spectrum radiation that is slightly more than half infrared. At zenith , sunlight provides an irradiance of just over 1  kW per square meter at sea level. Of this energy, 527 W

3193-456: Is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. Particularly intense near-IR light (e.g., from lasers , LEDs or bright daylight with

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3296-578: Is efficiently detected by inexpensive silicon photodiodes , which the receiver uses to convert the detected radiation to an electric current . That electrical signal is passed through a high-pass filter which retains the rapid pulsations due to the IR transmitter but filters out slowly changing infrared radiation from ambient light. Infrared communications are useful for indoor use in areas of high population density. IR does not penetrate walls and so does not interfere with other devices in adjoining rooms. Infrared

3399-491: Is energy in transit that flows due to a temperature difference. Unlike heat transmitted by thermal conduction or thermal convection , thermal radiation can propagate through a vacuum . Thermal radiation is characterized by a particular spectrum of many wavelengths that are associated with emission from an object, due to the vibration of its molecules at a given temperature. Thermal radiation can be emitted from objects at any wavelength, and at very high temperatures such radiation

3502-552: Is especially useful since some radiation at these wavelengths can escape into space through the atmosphere's infrared window . This is how passive daytime radiative cooling (PDRC) surfaces are able to achieve sub-ambient cooling temperatures under direct solar intensity, enhancing terrestrial heat flow to outer space with zero energy consumption or pollution . PDRC surfaces maximize shortwave solar reflectance to lessen heat gain while maintaining strong longwave infrared (LWIR) thermal radiation heat transfer . When imagined on

3605-440: Is flat white paint, with a high titanium dioxide content to maximize reflectivity. Some growers consider Mylar sheeting to be very effective when it lines grow room walls, along with Astrofoil (which also reflects heat), and Foylon (a foil-laminated, reinforced fabric). When growing indoors, the cultivator should maintain as close to an ideal atmosphere inside the grow-room as possible. The air temperature should be maintained within

3708-399: Is generally considered to be of inferior quality and/or grown with inferior technique. Cannabis grown is induced into flowering by decreasing its photoperiod to at least 10 hours of darkness per day. In order to initiate a flowering response, the number of hours of darkness must exceed a critical point. Generally the more hours of darkness each day, the shorter the overall flowering period but

3811-676: Is infrared radiation, 445 W is visible light, and 32 W is ultraviolet radiation. Nearly all the infrared radiation in sunlight is near infrared, shorter than 4 μm. On the surface of Earth, at far lower temperatures than the surface of the Sun, some thermal radiation consists of infrared in the mid-infrared region, much longer than in sunlight. Black-body, or thermal, radiation is continuous: it radiates at all wavelengths. Of these natural thermal radiation processes, only lightning and natural fires are hot enough to produce much visible energy, and fires produce far more infrared than visible-light energy. In general, objects emit infrared radiation across

3914-403: Is no universally accepted definition of the range of infrared radiation. Typically, it is taken to extend from the nominal red edge of the visible spectrum at 780 nm to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz. Beyond infrared is the microwave portion of the electromagnetic spectrum . Increasingly, terahertz radiation

4017-457: Is often the case, that the surrounding environment is cooler than the objects being viewed). When an object has less than perfect emissivity, it obtains properties of reflectivity and/or transparency, and so the temperature of the surrounding environment is partially reflected by and/or transmitted through the object. If the object were in a hotter environment, then a lower emissivity object at the same temperature would likely appear to be hotter than

4120-530: Is one of the primary parameters studied in research into global warming , together with solar radiation . A pyrgeometer is utilized in this field of research to perform continuous outdoor measurements. This is a broadband infrared radiometer with sensitivity for infrared radiation between approximately 4.5 μm and 50 μm. Astronomers observe objects in the infrared portion of the electromagnetic spectrum using optical components, including mirrors, lenses and solid state digital detectors. For this reason it

4223-526: Is required for strong floral development. A plant needs 1 or 2 months to mature before blooming. The plant is ready when it has revealed its sex. Plant size is a good indicator of sex. Females tend to be shorter and branchier due to their raceme type inflorescence than males, whose flowers grow in panicles . The males are then usually culled when they are identified, so that the females will not be pollinated, thus producing parthenocarpic fruits (popularly called " sinsemilla ", meaning "without seed"). During

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4326-471: Is required, except for cannabis grown with hydroponics or aeroponics . The optimal day temperature range for cannabis is 24 to 30 °C (75 to 86 °F). Temperatures above 31 °C (88 °F) and below 15.5 °C (60 °F) seem to decrease THC potency and slow growth. At 13 °C (55 °F) the plant undergoes a mild shock, though some strains withstand frost temporarily. Sun light or grow light can be used. Under artificial light,

4429-467: Is that low clouds such as stratus or fog can have a temperature similar to the surrounding land or sea surface and do not show up. However, using the difference in brightness of the IR4 channel (10.3–11.5 μm) and the near-infrared channel (1.58–1.64 μm), low clouds can be distinguished, producing a fog satellite picture. The main advantage of infrared is that images can be produced at night, allowing

4532-519: Is that the IR energy heats only opaque objects, such as food, rather than the air around them. Infrared heating is also becoming more popular in industrial manufacturing processes, e.g. curing of coatings, forming of plastics, annealing, plastic welding, and print drying. In these applications, infrared heaters replace convection ovens and contact heating. A variety of technologies or proposed technologies take advantage of infrared emissions to cool buildings or other systems. The LWIR (8–15 μm) region

4635-438: Is the dominant band for long-distance telecommunications networks . The S and L bands are based on less well established technology, and are not as widely deployed. Infrared radiation is popularly known as "heat radiation", but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that

4738-402: Is the most common way for remote controls to command appliances. Infrared remote control protocols like RC-5 , SIRC , are used to communicate with infrared. Free-space optical communication using infrared lasers can be a relatively inexpensive way to install a communications link in an urban area operating at up to 4 gigabit/s, compared to the cost of burying fiber optic cable, except for

4841-405: Is the period of greatest vulnerability in the life cycle of the plant, requiring moderate humidity levels, medium to high light intensity, and adequate but not excessive soil moisture. Most indoor growers use compact fluorescent or T5 fluorescent lights during this stage as they produce little heat. High-pressure sodium and metal halide lights produce large amounts of radiant heat and increase

4944-520: Is the spectroscopic wavenumber . It is the frequency divided by the speed of light in vacuum. In the semiconductor industry, infrared light can be used to characterize materials such as thin films and periodic trench structures. By measuring the reflectance of light from the surface of a semiconductor wafer, the index of refraction (n) and the extinction Coefficient (k) can be determined via the Forouhi–Bloomer dispersion equations . The reflectance from

5047-451: Is triggered by a hormonal reaction within the plant that is initiated by an increase in length of its dark cycle, i.e. the plant needs sufficient prolonged darkness for bract /bracteole development (flowering) to begin. Some Indica varieties require as little as 8 hours of dark to begin flowering, whereas some Sativa varieties require up to 13 hours. Watering frequency and amount is determined by many factors, including temperature and light,

5150-404: Is typically in the range 10.3–12.5 μm (IR4 and IR5 channels). Clouds with high and cold tops, such as cyclones or cumulonimbus clouds , are often displayed as red or black, lower warmer clouds such as stratus or stratocumulus are displayed as blue or grey, with intermediate clouds shaded accordingly. Hot land surfaces are shown as dark-grey or black. One disadvantage of infrared imagery

5253-436: The dipole moment , making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range. Infrared radiation is used in industrial, scientific, military, commercial, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without

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5356-463: The genus Cannabis in the family Cannabaceae . It may include three species, Cannabis indica , C. sativa , and C. ruderalis ( APG II system), or one variable species. It is typically a dioecious (each individual is either male or female) annual plant . C. sativa and C. indica generally grow tall, with some varieties reaching 4 metres or 13 feet. Female plants produce tetrahydrocannabinol (THC) (up to 31% by weight) as

5459-535: The IR spectrum is thereby divided varies between different areas in which IR is employed. Infrared radiation is generally considered to begin with wavelengths longer than visible by the human eye. There is no hard wavelength limit to what is visible, as the eye's sensitivity decreases rapidly but smoothly, for wavelengths exceeding about 700 nm. Therefore wavelengths just longer than that can be seen if they are sufficiently bright, though they may still be classified as infrared according to usual definitions. Light from

5562-488: The Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation that may be concentrated by a lens into a beam that the user aims at the detector. The beam is modulated , i.e. switched on and off, according to a code which the receiver interprets. Usually very near-IR is used (below 800 nm) for practical reasons. This wavelength

5665-652: The US. Illinois bans outdoor cultivation and requires growing in an enclosed and locked facility. Other states, like Michigan or Alaska, leave decisions about outdoor growing up to local governments. California, Vermont, and Massachusetts provide licenses for outdoor cultivation, often tiered based on size of operation. Vermont and Alaska also impose security restrictions on outdoor operations such as video surveillance, lack of visibility from roadways, and physical barriers. Where local laws do not permit growing cannabis, cultivators sometimes grow in forests or rugged and rural areas where

5768-765: The United States, all cannabis products in a regulated market must be grown in the state where they are sold because federal law continues to ban interstate cannabis sales. Most regulated cannabis is grown indoors. Occupational diseases , including asthma, are an emerging concern in the rapidly expanding U.S. cannabis industry. Cannabis cultivation and processing technicians may be exposed to numerous respiratory hazards, e.g. organic particulate matter and dust from ground cannabis flower, mold, bacterial endotoxins, and pesticides. Employees exposed to ground cannabis without adequate controls are at risk of developing occupational asthma which can be fatal. Cannabis belongs to

5871-412: The activation of hormones that trigger the expansion of the embryo within the seed. Then the seed coat cracks open and a small embryonic root emerges and begins growing downward (because of gravitropism ), if placed in a proper growing medium. Soon (after 2–4 days) the root is anchored and two oval cotyledons (sometimes called "false leaves" or "seed leaves") emerge in search of light and the remains of

5974-514: The age, size and stage of growth of the plant and the medium's ability to retain water. A conspicuous sign of water problems is the wilting of leaves. Giving too much water can kill cannabis plants if the growing medium gets over-saturated. This is mainly due to oxygen not being able to enter the root system. Anaerobic bacteria start to accumulate due to waterlogged, stale conditions. They begin to consume plant roots, beneficial (aerobic) bacteria, as well as nutrients and fertilizer. When using soil as

6077-648: The buds greatly increase in weight and size. Cannabis can be grown outdoors, either on natural soil or in pots of pre-made or commercial soil. Some strains perform better than others in outdoor settings, an attribute that depends on different conditions, variables and aspects. Outdoor marijuana strains, like most other strains, can be bought in numerous locations and over a hundred different cannabis strains that are bred for outdoor growing exist—many of these outdoor cannabis seeds are simply copies of other pre-existent strains or seeds with different names and descriptions. To generate optimum quantities of THC-containing resin,

6180-539: The division of infrared radiation into the following three bands: ISO 20473 specifies the following scheme: Astronomers typically divide the infrared spectrum as follows: These divisions are not precise and can vary depending on the publication. The three regions are used for observation of different temperature ranges, and hence different environments in space. The most common photometric system used in astronomy allocates capital letters to different spectral regions according to filters used; I, J, H, and K cover

6283-447: The energy from the Sun was eventually found, through Herschel's studies, to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an important effect on Earth's climate . Infrared radiation is emitted or absorbed by molecules when changing rotational-vibrational movements. It excites vibrational modes in a molecule through a change in

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6386-473: The eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the Wood effect that consists of IR-glowing foliage. In optical communications , the part of the infrared spectrum that is used is divided into seven bands based on availability of light sources, transmitting/absorbing materials (fibers), and detectors: The C-band

6489-499: The frequencies of infrared light. Typically, the technique is used to study organic compounds using light radiation from the mid-infrared, 4,000–400 cm . A spectrum of all the frequencies of absorption in a sample is recorded. This can be used to gain information about the sample composition in terms of chemical groups present and also its purity (for example, a wet sample will show a broad O-H absorption around 3200 cm ). The unit for expressing radiation in this application, cm ,

6592-480: The fruition (or fruiting ): the females inflorescences that were not pollinated (i.e.: fertilized by male pollen) start to produce infructescences that contain sticky white resin-containing glands (or trichomes ) in a final attempt for pollination by windborne male pollen. The trichomes produce resins that contain the largest amounts of THC and CBN , the two main psychoactive substances. Fertilized females continue to produce resinous trichomes but more plant energy

6695-485: The gray-shaded thermal images can be converted to color for easier identification of desired information. The main water vapour channel at 6.40 to 7.08 μm can be imaged by some weather satellites and shows the amount of moisture in the atmosphere. In the field of climatology, atmospheric infrared radiation is monitored to detect trends in the energy exchange between the Earth and the atmosphere. These trends provide information on long-term changes in Earth's climate. It

6798-411: The infrared light can also be used to determine the critical dimension, depth, and sidewall angle of high aspect ratio trench structures. Weather satellites equipped with scanning radiometers produce thermal or infrared images, which can then enable a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features. The scanning

6901-496: The infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nm or 9–14 μm) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their temperatures, according to the black-body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence

7004-412: The infrared wavelengths of light compared to objects in the background. Infrared radiation can be used as a deliberate heating source. For example, it is used in infrared saunas to heat the occupants. It may also be used in other heating applications, such as to remove ice from the wings of aircraft (de-icing). Infrared radiation is used in cooking, known as broiling or grilling . One energy advantage

7107-519: The inverse square law, but there are reasons to keep some distance from the canopy regardless of heat concerns; excessive light can cause bleaching of the plant material and the total canopy area contacted by light is decreased as the source is moved closer. Maximum efficiency should be obtained by maximizing the average light intensity (measured in PAR watts) per square foot times the number of square feet of plant matter contacted. Some cannabis cultivators cover

7210-516: The lamps falls upon the plants. Maximum efficiency can be obtained by creating a slightly concave canopy such that the periphery and centre of the canopy are both at the optimum distance from the light source. Often, the distance between lamp and plant is in the range of 0.6 m (2 ft) with high pressure sodium lamps, to 10 cm (4 in) with other lamps, such as compact, large and high-output fluorescent lamps. With proper cooling any light type can be moved extremely close to plants to combat

7313-604: The light cycle to 12 hours of darkness. Plant development increases dramatically, with the plant doubling or more in size. (See reproductive development below.) Production of more branches and nodes occurs during this stage, as the structure for flowering grows. The plant starts to develop bracts/bracteoles where the branches meet the stem ( nodes ). Pre-flowering indicates the plant is ready to flower. The flowering phase varies from about 6 to 12 weeks for pure indicas with their shorter flowering time than pure sativas. Mixed indica/sativa strains have an intermediate flowering time. The sex

7416-731: The local population is unlikely to find the crop. Cannabis is also grown hidden by a crop that is taller, such as maize. This is reported by the United States government to be common in the midwestern states. Bamboo and elderberry are also used as camouflage companion plants. Some government agencies, including the Drug Enforcement Administration (DEA), have claimed that in State and National Parks people have been injured by cannabis farmers protecting their crops using booby traps; no arrests or convictions for this had been made as of 2007 . Cannabis can be grown indoors in

7519-411: The lower the yield. Conversely, the fewer hours of darkness each day, the longer the overall flowering period and the higher the yield. Traditionally, most growers change their plants lighting cycle to 12 hours on and 12 hours off since this works as a happy medium to which most strains respond well. This change in photoperiod mimics the plant's natural outdoor cycle, with up to 18 hours of light per day in

7622-427: The most prized part of the plant. During the late period, the bract/bracteole are easily visible to the naked eye. Bract/bracteole development begins approximately 1–2 weeks after the photoperiod is reduced. In the first weeks of flowering a plant usually doubles in size and can triple. Bract/bracteole development ends around 5 weeks into flowering and is followed by a period of bract/bracteole “swelling”. During this time

7725-438: The name). A hyperspectral image is a "picture" containing continuous spectrum through a wide spectral range at each pixel. Hyperspectral imaging is gaining importance in the field of applied spectroscopy particularly with NIR, SWIR, MWIR, and LWIR spectral regions. Typical applications include biological, mineralogical, defence, and industrial measurements. Thermal infrared hyperspectral imaging can be similarly performed using

7828-405: The near-infrared spectrum. Digital cameras often use infrared blockers . Cheaper digital cameras and camera phones have less effective filters and can view intense near-infrared, appearing as a bright purple-white color. This is especially pronounced when taking pictures of subjects near IR-bright areas (such as near a lamp), where the resulting infrared interference can wash out the image. There

7931-446: The near-infrared wavelengths; L, M, N, and Q refer to the mid-infrared region. These letters are commonly understood in reference to atmospheric windows and appear, for instance, in the titles of many papers . A third scheme divides up the band based on the response of various detectors: Near-infrared is the region closest in wavelength to the radiation detectable by the human eye. mid- and far-infrared are progressively further from

8034-431: The observer being detected. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space such as molecular clouds , to detect objects such as planets , and to view highly red-shifted objects from the early days of the universe . Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, to assist firefighting, and to detect

8137-489: The overall quality and variety of commercially available cannabis over the past few decades. The Internet in particular has brought together widely diverse genetics from around the world through trading and purchasing. However, well-grown heirloom strains (e.g. island sweet skunk, fruity Thai etc.) are used to produce 1 gram; 1/28 oz per watt (g/W) harvest. Also called the stretch , this takes one day to two weeks. Most plants spend 10–14 days in this period after switching

8240-506: The overheating of electrical components. Military and civilian applications include target acquisition , surveillance , night vision , homing , and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm. Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops , remote temperature sensing, short-range wireless communication , spectroscopy , and weather forecasting . There

8343-455: The plant can flower even during long days. Although the flowering hormone in most plants (including cannabis) is present during all phases of growth, it is inhibited by exposure to light. To induce flowering, the plant must be subject to at least 8 hours of darkness per day; this number is very strain-specific and most growers use 12 hours of darkness. Flowers from certain plants (e.g. cannabis) are called bract/bracteole, and are (with cannabis)

8446-453: The plant needs a fertile soil and long hours of daylight. This means THC production for outdoor growth occurs optimally anywhere within 35° of the equator . Typical growing regions include Mexico, Nepal, Northern India, many parts of Africa, Afghanistan, the United States and Australia. In most places of the subtropics , cannabis is germinated from late spring to early summer and harvested from late summer to early autumn. Outdoor cultivation

8549-489: The plant typically remains under a regime of 16–24 hours of light and 0–8 hours of darkness from the germination until flowering, with longer light periods being conducive to vegetative growth, and longer dark periods being conducive to flowering. However, generally cannabis only requires thirteen hours of continuous light to remain in the vegetative stage. The 'Gas Lantern Routine' is an alternate lighting schedule that has proven to be successful for growing cannabis, while saving

8652-426: The radiation damage. "Since the eye cannot detect IR, blinking or closing the eyes to help prevent or reduce damage may not happen." Infrared lasers are used to provide the light for optical fiber communications systems. Wavelengths around 1,330 nm (least dispersion ) or 1,550 nm (best transmission) are the best choices for standard silica fibers. IR data transmission of audio versions of printed signs

8755-503: The range of 3-4000k. Cannabis plants also require both dark and light photoperiods , so the lights need a timer to switch them on and off at set intervals . The optimum photoperiod depends on each plant (some prefer long days and short nights and others preferring the opposite, or something in between). Recent advancements in LED technology have allowed for diodes that emit enough energy for cannabis cultivation. These diodes can emit light in

8858-414: The rate of transpiration in the plant which can quickly dry out seedlings with their small root systems. Duration: 1–2 months indoors. In this stage the plant needs a significant amount of light and nutrients, depending on the genetics of the particular plant. It continues to grow vertically and produce new leaves. The sex is starting to reveal itself, which is a sign that the next stage begins. Concurrently

8961-411: The root system expands downwards in search of more water and food. When the plant possesses seven sets of true leaves and the 8th is barely visible in the center of the growth tip, or shoot apical meristem (SAM), the plant has entered the vegetative phase of growth. During the vegetative phase, the plant directs its energy resources primarily to the growth of leaves, stems, and roots. A strong root system

9064-541: The season changes from summer to autumn. C. ruderalis is very short, produces only trace amounts of THC, but is very rich in cannabidiol (CBD) an antagonist to THC, which may be 40% of the cannabinoids in a plant. C. ruderalis flowers independently of the photoperiod with the main factor for flowering being the age of the individual plants. However, commercial cross-bred hybrids containing both ruderalis, indica and/or sativa genes exist (usually called autoflowering). Cannabis needs certain conditions to flourish. Soil

9167-434: The seed shell are pushed away. This marks the beginning of the seedling stage. Peat pellets are often used as a germinating medium because the saturated pellets with their seedlings can be planted directly into the intended growing medium with a minimum of shock to the plant. Imbibition of water through the membrane of the seed shell is the first step in the germination process for cannabis. Dry cannabis seeds are floating,

9270-574: The summer and down to less than 12 hours of light in fall and winter. Some 'semi-autoflowering' strains that have been bred exclusively for outdoor use, particularly in outdoor climates such as that of the UK, will start flowering with as much as 16–17 hours of light per day. Usually they can start flowering in July and finish far earlier than other strains, particularly those that haven't been bred as outdoor strains. Semi-autoflowering strains can be harvested before

9373-442: The telescope observatory at a high altitude, or by carrying the telescope aloft with a balloon or an aircraft. Space telescopes do not suffer from this handicap, and so outer space is considered the ideal location for infrared astronomy. Grow-ops Cultivation of cannabis is the production of cannabis infructescences ("buds" or "leaves"). Cultivation techniques for other purposes (such as hemp production) differ. In

9476-416: The temperature a bit. Assuming adequate light and nutrients are available to plants, the limiting factor in plant growth is the level of carbon dioxide (CO 2 ). Ways of increasing carbon dioxide levels in the grow-room include: bottled carbon dioxide, carbon dioxide generators, a milk jug and yeast solution (in which yeast grows in a container thereby emitting CO 2 ), a baking soda and vinegar mixture in

9579-479: The temperature of objects (if the emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry . Thermography (thermal imaging) is mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to greatly reduced production costs. Thermographic cameras detect radiation in

9682-455: The title SWIR . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=SWIR&oldid=1098629594 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Short-wavelength infrared It

9785-433: The use of hydroponics . To grow plants indoors, a growing medium (e.g. soil or growing substrate ), water , nutrients , light and air need to be supplied to the plant (with the exception of aeroponic cultivation, in which case a growing medium is not required). There are several different plant grow lights available. Currently the best source of light for cannabis remains to be metal halide or ceramic metal halide in

9888-427: The variety, they are usually determined by trial and error and fertilizers are applied sparingly to avoid burning the plant. Germination is the process by which a seed sprouts and a root emerges. Germination in cannabis can occur in as little as twelve hours or can take as long as eight days, depending on the cultivar and environmental conditions. Warmth, darkness, and moisture initiate metabolic processes such as

9991-406: The vegetative phase, cultivators generally employ an 18- to 24-hour photoperiod because the plants grow more quickly if they receive more light, although a warmer and cooler period are required for optimal health. Although no dark period is required, there is debate among cultivators as to whether a dark period is beneficial, and many continue to employ a dark period. Energy savings often support using

10094-414: The vegetative stage, as well as a complete micronutrient fertilizer. The strength of the fertilizer is gradually increased as the plants grow and become more hardy. Advanced cultivation methods include: The emphasis on advanced cultivation techniques, as well as the availability of hybrid strains (with names like Northern Lights , Master Kush , NYC Diesel ), is believed to be a factor in the increase in

10197-476: The visible light filtered out) can be detected up to approximately 780 nm, and will be perceived as red light. Intense light sources providing wavelengths as long as 1,050 nm can be seen as a dull red glow, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and

10300-472: The visible spectrum. Other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (the common silicon detectors are sensitive to about 1,050 nm, while InGaAs 's sensitivity starts around 950 nm and ends between 1,700 and 2,600 nm, depending on the specific configuration). No international standards for these specifications are currently available. The onset of infrared

10403-444: The walls of their grow-room with some type of reflective material (often Mylar or Visqueen), or alternatively, white paint to maximize efficiency. One commonly used covering is 150 μm (6 mils) PVC plastic sheeting that is white on one side and black on the other. The plastic is installed with the white side facing into the room to reflect light, and the black facing the wall, to reduce fungus and mold growth. Another common covering

10506-441: The weather in northern latitudes becomes very wet and cold (generally October), whereas other strains are just finishing flowering, and may suffer from botrytis (grey mold) caused by wet weather. Alternatively growers may artificially induce the flowering period during the warmer months by blacking out the plants for 12 hours a day i.e. by covering the plants with black plastic for example, which excludes all light during this period so

10609-411: Was long known that fires emit invisible heat ; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered that infrared radiation is a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer . Slightly more than half of

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