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Topic: Light-hour

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Light year - Wikipedia, the free encyclopedia Since the speed of light in a vacuum is exactly 299,792,458 m/s by the definition of metre, one light year is exactly equal to 9,460,730,472,580,800 m. More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely far away from any gravitational or magnetic fields, in one Julian year (365.25 days of 86400 seconds each). Units related to the light year are the light minute and light second, the distance light travels in a vacuum in one minute and one second, respectively. en.wikipedia.org /wiki/Light_year   (484 words)

Light hour - Wikipedia, the free encyclopedia A light hour (also written light-hour) is a unit of length. It is the distance travelled by light in vacuum in one hour. en.wikipedia.org /wiki/Light_hour   (78 words)

Houseplants - Needs - Proper Light Light duration refers to the number of hours of light that falls on a plant in 24 hours. Light intensity refers to brightness and is measured in foot-candles, which is defined as the amount of light that one candle produces, measured one foot away. Light is essential for plant growth and can be one of the most limiting factors for success with houseplants. www.urbanext.uiuc.edu /houseplants/needs_light.html   (368 words)

FAQ: Plant Lighting All plants have a cycle in which during the light hours they use CO and release Oxygen through a process called photosynthesis. If the light time exceeds 16 hours more wattage should be added to reduce this time, Or if the light time is less than 8 hours less wattage must be used to allow adequate time for photosynthesis. Fluorescent lighting is the most economical means of establishing a broad spectrum of light in an adequate quantity for the survival of aquatic plants. faq.thekrib.com /plant-lighting.html   (816 words)

Light for Backyard Flocks Light broilers 24 hours per day for the first 3 weeks at a level of 2 to 3 foot candles. This means that if you had a young flock of layers in production at this time you should provide a total of 15 1/2 hours of light for the flock as long as they lay -- natural light plus enough artificial light to total 15 1/2 hours per day. The light is received by the eye of the bird and is conducted by the optic nerve to the brain which in turn stimulates the pituitary gland. www.umext.maine.edu /onlinepubs/htmpubs/poultry/2227.htm   (651 words)

Let There Be Light It is the increase of light from 14 to 16 hours, rather than same amount of light daily, that turns birds on. Studies on some species show that at least 9 hours of light a day are needed for production of hormones and the sexual organs to begin to become functional. The amount of light in a day (photo-period) is the major controlling factor in spermatogenesis of the male bird. www.realmacaw.com /pages/light.html   (654 words)

Worm's Way Tips & Tricks - Indoor Lighting Principles  More than 12 hours of light will prolong flowering, but a shortened or interrupted period of darkness through the use of dim lighting, inadvertent ambient light pollution, or even by suddenly opening the door to your indoor garden, can confuse the plants and cause them to try to revert to a vegetative growth stage. It is possible to gradually decrease the daylight hours while increasing the dark period to simulate a natural photoperiod, but this is not neccessary and usually delays flowering by several weeks. Remember that light is most intense in the center of the garden area, and becomes less intense as it radiates away from the bulb. www.wormsway.com /articles/04_03_IndoorLightingPrinciples.asp   (926 words)

CannaStats - Low Maintenance Mothering Manipulating light timer settings in such a way as to provide 12 hours of light over a 24 hour period, but not permitting 12 hours of uninterrupted darkness to occur, can reduce growth by 25% when compared to the traditional 16 hour vegetative photoperiod without triggering the flowering response. Needless to say 16 hours of light per day will produce less growth than more hours will, so for purposes of growth reduction fewer hours of light per day is preferable. As you can see from the below graphic, over a 24 hour period these timer settings will provide 12 hours of light and 12 hours of darkness, but will not trigger flowering because no single dark phase is long enough to do so. www.angelfire.com /cantina/fourtwenty/articles/mothering.htm   (733 words)

UNODC - Bulletin on Narcotics - 1975 Issue 2 - 003 However, where the 1 hour of light was placed near the middle of the dark period, flowering was 50 to 100 per cent, and stems averaged several millimeters longer than those of the 15-hour controls. Because a 6-hour light and 6-hour dark sequence results in flowering, and a 12-12 sequence does not, a photoperiodic schedule was sought in which a small amount of light spaced in the middle of a long dark period would promote flowering. At the end of the 12 hours, all plants, except the 12-hour controls, were given eight more hours of light at a range of intensities from 65 to 2, 152 lux. www.unodc.org /unodc/fr/bulletin/bulletin_1975-01-01_2_page004.html   (3266 words)

Clinical & Research News Light of this intensity and daily duration is widely used in research studies and as maintenance therapy for people with winter depression. Lewy is investigating whether a small dose of melatonin in midafternoon—.5 mg or less—can serve as an alternative to light therapy or permit a reduction in duration of morning light exposure. Light therapy at the right time on the biological clock induces rapid remission in 80 percent of persons with winter depression, scientists at the New York State Psychiatric Institute (NYSPI) and Columbia University have found. www.psych.org /pnews/01-03-16/best.html   (1089 words)

Testing "Chic Lites" For the next 19 weeks, one group was exposed to four hours light (L) and 20 hours dark (D), six L and 18 D, eight L and 16 D, and 10 L and 14 D. Production was closely monitored on all the birds from 20 to 50 weeks of age. For their first 140 days of life broiler breeder replacement chicks are routinely exposed to a strict regimen of eight hours of light and 16 hours of darkness during this "preproduction" period. Hens in the four hours of light group produced 123 eggs during the 20- to 50-week production cycle, compared to 131 eggs for 8 L-16 D and 10 L-14 D and 132 for the 6 L-18 D group. www.ag.auburn.edu /aaes/webpress/1990/chiclights.htm   (531 words)

docs\lectsupl\Light\light light is the layman's term for visible radiant energy in the 400 to 700 nm wavelength region of the spectrum. The 400 to 700 nm wavelength band of radiation (visible light) from the sun passes through the atmosphere relatively unaffected before reaching the earth's surface, whereas other wavelengths (especially UV and IR) are absorbed, reflected or scattered by the atmosphere. Horticulturist manipulate the light and dark periods to which plants are exposed in order to trigger photoperiodic plants to flower during any season of the year. generalhorticulture.tamu.edu /lectsupl/Light/light.html   (1268 words)

ACF Indoor Plant Grow Light Information Guide The exception to this is using HPS grow lights in a greenhouse or in conjunction another light source that emits light in the blue spectrum. These lights are good for providing supplemental light to individual house plants or small groups of plants and provide an inexpensive alternative to other grow lights, because they do not require a ballast. The bulb will light up beyond this time but due to the gradual decline of light, it is not worth your while to wait for the bulb to finally burn out. www.littlegreenhouse.com /guide3.shtml   (1006 words)

Housing and Supplemental Lighting It appears that 16 to 18 hours of light with an intensity of between 15 and 25 foot candles is necessary. In a second trial cows were housed in stanchions and provided with 16 hours of light or natural light of between nine and 12 hours duration. One group of 20 cows was exposed to 18 hours of light and six hours of darkness for 84 days. www.canr.msu.edu /msue_thumb/articles/light_milk.html   (702 words)

Untitled Document Study Methods: Controlled lab experiments using fluorescent lights, tanks, oxygen consumption measuring apparatus, and a feeding activity recorder under five different experimental light conditions: natural light conditions, continuous light, continuous dark, 12 hours light : 12 hours dark, and 6 hours light: 6 hours dark over five day periods. Light and feeding activity: under natural control conditions, feeding was greater during the morning than at night. The influence of light as an exogenous factor is not clear. depts.washington.edu /newwsdot/ali2.html   (273 words)

Flashlights and LED lighting One hour of sun on a 10 watt solar module can charge a battery enough to run this light for over 15 hours. Light output is only 11 lumens, but this lamp allows you to make a solar lighting system with a very small solar module and battery. This is a great light for cavers, backpackers, boaters and anyone who does not want to carry a lot of batteries and wants dependable light. www.advancedenergyonline.com /catalog/applications/Flashlights.htm   (700 words)

Harvard Gazette: When light has you singing the blues After 6.5 hours of exposure, blue light readjusted their body clock by 3 hours, green light by about 1.5 hours. Steven Lockley and his colleagues found that blue light is more efficient at resetting biological clocks than standard white light, a discovery that could help jet-setters, shift workers, astronauts, students, and military personnel. Until 1995, dogma held that the intensity of light striking receptors that give humans color vision also adjust the daily cycle that controls sleep, performance, and other physical and behavioral factors. www.news.harvard.edu /gazette/2003/09.25/01-light.html   (1171 words)

Botany online: Plant Responses - Light - Photoperiodism - Stimulation of Flowering After a light period of eight hours are dark periods of 24 hours or a multiple of 24 hours optimal. A reduced light program where the plant receives just a few hours of light every 72 hours is enough to synchronize the alternation of skotophile and photophilic phase. After 9-12 hours of light is the development of the plant inhibited by all further exposure to light: the plant enters its www.biologie.uni-hamburg.de /b-online/e30/30c.htm   (1122 words)

3RLIGHTING: FAQ Hydroponics Grow Light The typical rule of thumb for flowering plants is to run a 16 to 18 hour light cycle then 6 to 8 hours of dark time, during the vegetative stage. This is why the light is often cut back during Bloom stage. It is also typical to run a Metal Halide during the Vegetative stage then switch to a High Pressure Sodium Light during the Bloom stage. www.3rlighting.com /html/3rlighting030.htm   (323 words)

Daylight shock For instance, a plant that flowers under a dark period of 11 hours can be grown vegetatively under a period of 9 hours of darkness and 15 hours of light without fear of it flowering prematurely. Clones grown under a regimen of 18 hours of light with a 6 hour dark period are less likely to be shocked into flowering when they are placed outdoors. Should the clones I am going to plant outdoors grow under continuous fluorescent light, or should I root them under 18 hours of light? www.cannabisculture.com /articles/2381.html   (505 words)

CAVE GROWING We have concluded that four hour light daily was an extremely good amount of time for the plant to grow with the least amount of light possible, we had the most amount of growth in the pots under the four hour light. By researching light intensity needed for good plant growth we discovered that 6 hours is needed at the least for a plant to grow and be healthy. We said that the twelve hours of light a day would be the most effective, when in fact four hours of light was the best for the growth of plants. www.ri.net /schools/Narragansett/NHS/scienceweb/webpages00/PerG/caveG/CAVE.htm   (667 words)

siopes.htm All hens held on 12.5 or more hours of light per day became photorefractory as indicated by a lack of response to a boost in day length to 20 hours of light per day (Figure 4). After 24 weeks of light treatments all hens were abruptly exposed to 20 hours of light per day (20L:4D) and photoresponsiveness (Photorefractoriness) was evaluated, by original light treatment group, for the following four weeks based on the relative change in egg production. The light treatments were given during winter and summer seasons in separate experiments and optimal egg production was evaluated by two indicators: time to reach 50% hen-day production and cumulative eggs per hen to 13 and 24 weeks of photostimulation. www.cals.ncsu.edu:8050 /course/po420/siopes.htm   (862 words)

Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos Those numbers refer to the amount of light and dark that the plant receives (18 hours of light / 6 hours of darkness). Anything above 14 hours of light per day will keep the plant in vegetative mode-- growing leaves and not buds. Those 6 hours of darkness can be timed to happen during the hottest part of the day, providing some relief for growers in hot climates. www.overgrow.com /growfaq/788   (182 words)

Inventions light bulb of light hours at the same price per light hour by producing half as many as the new light bulbs as he or Bottom line: higher profits from using the invention. (Image © Archive Photos) The first electric light bulb, invented by Thomas Edison, had carbonized thread as its filament, and burned for 45 hours. light bulb ever crafted, and technology continues to change every day, Edison's work with light bulbs was a spark of brilliance on the timeline of invention. getinfoeasy.com /q/inventions-light-bulb.html   (1294 words)

TS&P 2 Also, strips of aluminum foil may be placed in the garden around plants requiring long hours of light to reflect more light toward the plants. Long-day plants require 14-18 hours of light and include beets, onions and spinach and most annuals. There must be the proper number of consecutive hours and amount of light that our plants receive. aggie-horticulture.tamu.edu /galveston/ts&p_2.htm   (413 words)

How to force flowering This is 2 hours longer than the 12 hour light period which is generally recommended. The two hours extra light each day is a 16 percent increase in light to the plant. Should the drop between 18 hours of light and 12 hours of light be gradual or immediate? www.cannabisculture.com /articles/2053.html   (399 words)

ESB > News and Events > ESB Provides 50 Hours of Light or 12 Hours' TV - All for 10.71 Cents 10 hours of light with a 100 watt bulb. 50 hours of light with a 20 watt CFL bulb. ESB > News and Events > ESB Provides 50 Hours of Light or 12 Hours' TV - All for 10.71 Cents www.esb.ie /main/news_events/press_release128.jsp   (170 words)

IMO LED Lights Page Super bright white light, incredible run times, Nite Hawk engineered and patented total internal reflection (T.I.R.) optical lens, multiple power settings and an estimated Emitter life of 100,000 hours are a few of the features that make the new Nite Hawk ECO headlamp truly remarkable. After 3 seconds, the next push of the smart switch turns the light off (instead of cycling through light levels) and remembers which level you were using the next time you turn it on. Burntimes: Xenon, 12 hours; LEDs, 24 hours (and this is at constant brightness; they'll continue to burn at decreasing levels for days afterward). www.caves.org /imo/LED.htm   (5864 words)

GLS Section:TA BackCountry Tips Frames This gives more than 12 hours of dim light from 2 AA nicads. Monster Maglite:- 4 D nicads -> 5 hours light bright enough to fry low flying aircraft. The greatly extended battery life coupled with adequate light output for in-tent use means that this is the way I shall go for in-Landrover/tent use, and for an emergency backup light for caving. angeles.sierraclub.org /gls/frames/T5.htm   (328 words)

RGJ.com - LEDs will take you light years ahead By comparison, an incandescent flashlight such as the Mini Maglite gives four to six hours of light on one set of batteries, and its bulbs last between 10 and 30 hours. Because of their light weight, durability and long life, LEDs are bound to replace traditional incandescent headlamps and other lights for most uses. By 28 hours, the Tikka’s beam was down to about 27 percent of its original strength and wasn’t really useful. www.rgj.com /news/stories/outdoors/983406555.php   (635 words)

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