Question

A red and a green pencil are taken in a room illuminated with green light. In the room
A. Both pencils will appear dark.
B. Pencils will appear as red and green respectively.
C. Red pencil will appear dark and green pencil as green.
D. Red pencil will appear red and green pencil dark

Answer 1

Hint: White light is composed of many wavelengths from red to violet. Red color absorbs all the other colors except red. In the same way green absorbs all the colors except green. So when the colors are illuminated with different colors other than the actual color, they absorb the different colors. Use this info to answer the given question.

Complete step by step answer:
We are given to find what happens to a red and a green pencil when they are taken in a room illuminated with green light.
Color of a substance arises by absorption of visible light.
Visible light or white light is composed of varying wavelengths of light. Its range is 400nm to 700nm. Different wavelengths appear differently to our eyes in different colors.
When a light of wavelength x falls upon another light of wavelength y, then it absorbs the wavelength x and forms a different color. In the same way red absorbs all the other colors except red and green absorbs all the other colors except green.
So when a red pencil and a green pencil are kept in a green room, then green pencil reflects the green color and red pencil absorbs the green color.
Therefore, the green pencil appears green and the red pencil appears dark.

Hence, the correct option is Option C; Red pencil will appear dark and green pencil as green.

Note: Red reflects red, green reflects green, blue reflects blue and so on. So when a light of some wavelength falls upon light of the same wavelength, then the light reflects. We perceive the color of any object because that object reflects the light of its color only. Be careful with the absorption and reflection.