Question

A green leaf placed in a dark room is illuminated by a red light. The leaf will appear to be
A) Green
B) Red
C) Yellow
D) Black

Answer 1

Hint: Recall that there are seven colors in the white light. These colors are collectively called the spectrum of white light. They are named as violet, indigo, blue, green, yellow, orange, and red. These colors can also be called VIBGYOR. The phenomenon of reflection will be followed here.

Complete step by step answer:
VIBGYOR, Out of these seven colors of light, violet has the shortest wavelength and red has the longest wavelength. Whenever a ray of light falls on a substance, then either it reflects the light or absorbs the light. It is known that this light has seven colors.

The color which is reflected by the substance appears to be its color to a human eye. All other colors are absorbed by the substance and are not visible to the eye.

It is given that the leaf has a green color, therefore it will reflect only green light and absorbs the rest of the colors. But when the red light is made to fall on the leaf, then the leaf will absorb the red light. Therefore, no light will be reflected and the leaf will appear black.

Hence, Option D is the right answer.

Note:
It is to be noted that the absorption of light also depends on frequency apart from the wavelength. The absorption of light is directly proportional to the frequency of light. But the wavelength is inversely proportional to frequency. A color with the longest wavelength has a minimum frequency and color with the shortest wavelength has a maximum frequency. Therefore, the violet color will have maximum frequency while the red color has the least frequency.