What unit is used to measure brightness? please answer..?
455244
Photometry is the science of measurement of light, in terms of its perceived brightness to the human eye. It is distinct from radiometry, which is the science of measurement of light in terms of absolute power.\n\nPhotometric measurement is based on photodetectors, devices (of several types) that produce an electric signal when exposed to light. Simple applications of this technology include switching luminaires on and off based on ambient light conditions, and light meters, used to measure the total amount of light incident on a point.\n\nFor complete details refer\nhttp://en.wikipedia.org/wiki/Photometry_%28optics%29
698812
lumen measures the intensity of light and nanomters measures the weavelength of the light\nthe shoter the wavelength the bluer/purpler the colour
325557
you could actually use the cable, you can also buy a cable tester, where you plug both ends in, run the test and some status LED's will give you the results\n\nhttp://www.maplin.co.uk/Module.aspx?ModuleNo=45778&doy=6m4&C=SEO&U=Template
320485
What kind of detector?
372456
To measure ohms, DCV, ACV, Amps or what????
172519
Sorry....that is not correct.  LCD's do NOT emit light.\n\n\nYou see LCD technology does not itself emit light. you either must have enough ambiant light to see, or it must be 'back-lit'. The Technology formmerly used to do this was CCFL or Cold Cathode Forescent Lamp, these failed in 2 different ways as they aged.\n\n1. the light would get darker as it aged. Some would even change color therby messing-up the colors the display rendered.\n\nand\n\n2. As the bulb ages, it requires more and more power to engergize it. Eventually it will reach a point where the amperage required to start the lamp, will exceed the capacity the circut it is on can provide and simply not light.\n\nIf you've ever seen this, or suspect that this is your problem (display won't light, or goes dark shortly after starting,) simply shine a bright light source directly into the display, you should see faintly whatever the desktop was diplaying at the time.....or your desktop if it never came on to begin with.\n\nCurrent Backlight technology uses white LED lights....far better.\nthe BEST ones use 3 LED lights....1 each of Red Blue and Green, much much better at displaying the full color spectrum.\n\nHope that helps !\n\nPS: the FLASHLIGHT you have.....is an LED flashlight, I would wager. I have one too, they're great !  $27 bucks though.\n\nPPS: more like 100,000 hours.\n\n\nto poster below....the current back-lighting method IS LED, the fact that it is also used in Thin Film Transister Displays does not really make a difference to this question.\ncheck your facts. oh and your 'plasma' info is waaaaaay off.\none year!  ha.
171185
use black light,u will find it in any good store
135378
Try a black light.\n\nIn forensic investigations, black lights are used to reveal the presence of trace evidence, such as blood, urine, semen and saliva, by causing visible fluorescence in these substances
957818
I work with light bulbs and the light output is measured in C. lumens.
735927
Funny you should ask,,I just bought one ,with the recomendation of a friend and am about  to take a test in about an hour or so..ill probablly get the resultsmon..and will try to let you know..
210187
Simply put:  it is the luminous intensity expressed in candelas. ( the brightness of light compared to a candle)\n\nA candela is a measurement of the intensity of light, used in the International Standard (SI) measurement system. In the modern age, it is technically defined as the intensity in a given direction of a source that emits monochromatic radiation of a frequency of 540 x 10^12 hertz and which has a radiant intensity in the same direction of 1/683 watts per steradian.\n\nThe candela as a unit of measurement grew out of the desire to adopt a standard method to measure light. In the 19th century, each country had its own measure of light, most extremely difficult to reproduce with accuracy. At the beginning of the 20th century, groups of nations began adopting new standards, such as the international candle, which were based on a single type of lamp and much more consistent. Eventually, in the 1930s, it was decided that a more precise definition was needed.\n\nInitially, the candela was defined as the luminous emission of a Planckian radiator, a type of blackbody, at the temperature of freezing platinum (2045 K). This correlated roughly to the light emitted by a typical candle, making it a suitable measure. In the late 1970s, it was determined that the experimental difficulties in creating a Planckian radiator at such high temperatures made the existing definition of candela less than desirable. The new breakthroughs in radiometry allowed scientists to have a more specific definition, and so the current hertz/watts definition of candela was adopted.\n\nOne reason the watt was not initially tied to the candela is the eye’s differences in seeing various wavelengths of light. Since the human eye is less observant of blue and red light, more wattage is needed to produce the same result in the brain as with yellow or green light. This is why the definition of candela is defined as a very specific hertz, unachievable in actual common lighting. There are those who critique the modern definition of the candela for this reason, arguing that it has removed any common-sense understanding of the candela as an actual emission of light.\n\nThe reason the modern definition of candela includes the somewhat bulky 1/683 watts per steradian is to make it conform to the previous definition, in order to avoid any confusion when comparing the modern unit to the historical candela. In this context, the steradian is the cone of light as it emerges from the source, such that it would light up one meter square of the inside of a sphere with a one meter radius.\n\nSince the precise definition is so unwieldy, it is not uncommon in standard usage to see the candela referred to as “roughly” the amount of light generated by a single candle. This definition is perfectly suitable for common usage, as is the translation of 120 candela to roughly the light emitted by a 100 watt light bulb.
433589
Okay, wait a minute... what's a bright?
1109328
That happens because of the built-in power saving feature which reduces the brightness when the computer is running on battery power.  Usually you can increase the brightness by pressing the <Fn> key and the key with the picture of the 'sun and up-arrow' for brightness increase control.  Check the manual if you are unsure.
808047
By touching the lamp you are changing the capacitance of the lamp and a circuit inside the lamp detects the change and turns on the light. \n\nIn order to offset sensitivity to temperature and other objects near the lamp it is designed to be triggered by a sudden change in capacitance - so when you slowly touch it, or tap it with an object with insufficient cpacitance then the circuit does not detect enough of a change to trigger.
354014
what sort of sensors are u interested in. if it is light then it can be measured using photoconductive or ptotovoltaic devices.
3690
The ones i've seen are a diode with 1 or 2 little arrows pointing out, indicating radiant light.  The circle is optional.\n\nSimilarly, photodiodes have the arrows pointing in.
55652
light density or intensity? if you're talking about intensity then it depends on distance. that's an inverse square relationship.