2007-06-22 09:12:04 · 18 answers · asked by scott g 1 in Science & Mathematics ➔ Physics
Usually lumens or foot-candles for intensity, and (oddly enough) degrees Kelvin for colour 'temperature'
2007-06-22 09:15:50 · answer #1 · answered by maddog27271 6 · 2⤊ 0⤋
Light is energy, which is measured in watts, but what matters for us is the amount energy that falls on the specific area of our eye. Thus, we measure the energy that falls on a given area as a measure of the light intensity. Thus we talk of brightness, or luminous intensity. The area of our eye is fixed. If we stand close to a light, it seems bright. If we move a long distance away, it is much dimmer, or we may not see it at all. As the light spreads out, so the energy falling on our eye gets smaller.
So we can measure luminous intensity in terms of watts per square metre, say. Now, in physics, it has been shown that luminous intensity falls off with the inverse square of the distance between source and observer. What does that mean? Suppose we have a square, white screen that is exactly one metre along each side. If we hold the screen 1 metre away from a light source, let's say the energy falling on that square metre is 400 watts. If we now move the screen to a distance of 2 metres, the light intensity falling on the screen is now 400/(2 x 2) = 100 watts. Increasing the distance to 4 metres results in a decrease of the light to 400(/4 x 4) = 25 watts. And so on...
2007-06-23 02:35:51 · answer #2 · answered by Anonymous · 0⤊ 1⤋
Luminous intensity is the power of light from the source measured in Candela
Luminous flux is the light emitted by a source and is measured in Lumens
Illuminance is a measure of the density of luminous flux at a surface measured in Lux ( lumens per square metre)
Luminance is a measure of the light reflected from a surface measured in Candela per metre squared
2007-06-22 10:28:48 · answer #3 · answered by Anonymous · 1⤊ 0⤋
I assume you're asking about candle power and not the speed of light. You are not clear on this. I'm going back 60 years now but if I remember correctly, it's 300x10 to 6th power in metres per second for the speed. I'll quite rightly be corrected very quickly if I'm wrong.
2007-06-22 09:27:17 · answer #4 · answered by LEONARD W 4 · 0⤊ 1⤋
POWER is measured in Watts
ENERGY is measured in Joules
(1 Watt = 1 Joule per second)
Sorry Beauty Spot im just being picky
Just thought id clear that up... lol
2007-06-24 02:31:29 · answer #5 · answered by russfussuk 3 · 0⤊ 1⤋
Lumens, candellas & watts for power, Kelvin or nanometres for 'temperature / colour'
2007-06-22 09:23:22 · answer #6 · answered by creviazuk 6 · 0⤊ 0⤋
hey scott...this is Abhilasha Kumar frm India.
the answer of ur question is -The speed of light is measured in either in m/sec or km/hr.
2007-06-23 01:21:53 · answer #7 · answered by AbhiK 1 · 0⤊ 1⤋
Light travels at different wavelengths and is measured in nanometres (nm)
2007-06-22 09:15:48 · answer #8 · answered by Anonymous · 0⤊ 2⤋
Lumins or candle light.
2007-06-22 09:16:22 · answer #9 · answered by Telemon 3 · 1⤊ 0⤋
If memory serves, Lumens!
2007-06-22 09:28:47 · answer #10 · answered by jono_unwin 1 · 0⤊ 0⤋