Why does yellow object appear yellow under red light ?

Question

I am using ray box and with red filter and the light reflected on a yellow object. A red light is reflected..Why ?

Answer 1

Chances are that the red filter you are using also lets some yellow light through. Most colour filters allow a range of different wavelengths to pass through them with varying succcess, i.e. a blue filter blocks out the red end of the spectrum, but may let some green light through. Have a look at http://www.rosco.com/australia/filters/supergel.asp#Colors to see the transmission spectra of different filters used in theatre lighting. Remember that ~430 nm is violet, ~540 nm is green, ~590 is (sodium) yellow and ~630 + is red.

The same applies to light reflected by objects. Most objects reflect a spectrum of colours. When white light shines on them, they appear to be the colour that is reflected the most by the object. If you remove that colour from light shining on the object, the object will appear to be a different colour. If all the colours that the object reflects are removed from the incoming light, the object will appear black.

For example, a yellow object may also reflect some red and some green light. By using a red filter, you are removing the green and yelllow components from the light, and so only red light can be reflected by the object. If you shone blue or purple light on the yellow object, it would appear black as the object does not reflect those colours.

Answer 2

Because yellow light is actually made from red and green light (this sounds weird because if you mix red and green paint you do not get yellow paint but it is still true), therefore when you filter through only the red light you see red reflected.

Answer 3

Infrared Rays,

Answer 4

It might appear more a light orange which could look yellow

Answer 5

:-? it's a mistery