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Q & A: Seeing reflected and emitted light

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Most recent answer: 10/23/2016
Q:
Why do we see the colour of an object corresponding to the wavelengths that it reflects and not the one corresponding to the wavelengths emitted by it?
- Meha (age 18)
Noida ,Uttar Pradesh,Indis
A:

You see both! Many everyday objects don't emit visible light, but most of them reflect it. Here are some examples:

1. A cat emits some infrared light because of its temperature, but you can't see that without a special camera. It emits almost no visible light, so you only see the color of light that reflects off it.

2. An incandescent light bulb emits a lot of visible light (and even more infrared light) because of its hot filament (~2500 C). You see the color of that emitted light, plus any light that happens to reflect off the bulb, although the emitted light is probably much brighter.

3. Some minerals are fluorescent and will glow under a black light (UV). The high-energy UV photons from the black light excite atoms inside the mineral, and the excited atoms emit photons of visible light.

So, it just depends on the object—some emit visible light and some only reflect it.

Here's a similar question you can look at as well: http://van.physics.illinois.edu/qa/listing.php?id=27500

Rebecca H.


(published on 10/23/2016)

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