Chapter 16, Problem 68A

To determine

The color one can see on the white wall when it is lit by the flashlight which is wrapped with red and green cellophane.

Answer to Problem 68A

Black

Explanation of Solution

Introduction:

The color filter transmits the light of its own color and absorbs all other colors of incident light. If two filters are used together, then the light transmitted through the first filter gets absorbed by the second filter. Hence, there is no light transmission through the second filter.

It is given that the flashlight is wrapped with two cellophanes − red and green. The red cellophane transmits the red color and absorbs all other colors of light from flashlight. This red color transmitted by the red cellophane would be absorbed by the green cellophane and hence there is no light transmitted through the green cellophane. Thus, the black color will appear on the white wall.

Conclusion:

Therefore, black color can be seen on white wall for the given situation.