Question

A rose appears red in white light. How will it appear in (i) green light, (ii) red light? Give a reason for your answer each.

Answer 1

Hint: Learn how we see objects with our human eye, how we see and differentiate between colours. When light falls on an object that gets reflected by the object that light falls into our eye then we can see that particular object.

Complete answer:
We know that when some light falls on a body it gets reflected in every direction, due to this reflection light falls into our eyes and we can see that object. Now, this reflection of light depends on the type of material. With different types of material the light may get reflected or may get absorbed by that particular matter.

So, if we see an object in a particular colour since only that colour is reflected by the object and rest of the colours are absorbed by the object. So, when white light falls on an object depending on the type of object we can see colours as white light contains all the colours of light. So, when a white light falls into a rose only the red colour gets reflected and the rest of the colours are absorbed by the rose. So, we see the rose as red.

(i) When green light falls on a rose: Since green light is a monochromatic light it does not contain the red colour hence it gets absorbed by the rose. So, no colour is reflected from the rose and we see the rose as dark or black.
(ii) When red light falls on rise: It gets reflected back totally as no other colours are there in red light, so the rose appears to us as red in red light.

Note: In quantum or atomic level the molecules actually the electrons in lower state absorbs those colours of light which has an energy gap in equal to \[E = h\nu \], to jump to a higher state or has the same frequency of vibration as the electron. So, a rose does not contain many electrons which have an energy gap equal to the energy of a red colour light. So, that most of that colour gets reflected or refracted so we see that colour of light when falling on to that particular object.