Question

A piece of cloth looks red in sunlight. If it is held in the blue portion of a solar spectrum, it will appear
(A) Red
(B) Black
(C) Blue
(D) White

Answer 1

Hint :Black objects absorb all colours so no light is reflected back. White objects appear white because they reflect all colours. When a piece of red cloth is held in only the blue portion of the spectrum, red cloth absorbs the blue light and since there is no red light to be reflected, therefore no colour will be reelected back, that cloth piece will appear black.

Complete Step By Step Answer:
In the question it is given that the cloth looks like red in sunlight because it absorbs all the colours of the sunlight except red light that is why red light is being reflected back to our eyes.
Now according to the circumstances when a piece of red cloth is held in only blue portion of the spectrum, red cloth absorbs the blue light and since there is no red light to be reflected, therefore no colour will be reflected back that is cloth piece will appear black. Black objects absorb all colours so no light is reflected back. White objects appear white because they reflect all colours.
Hence B is the correct answer.

Note :
Black objects absorb all colours so no light is reflected back. White objects appear white because they reflect all colours. There is no reflection when no colour is absorbed. Here red colour is not reflected and no blue colour to be absorbed.