Question

Two identical plates are placed on top of a snow bank on a sunny day. One is of black color and another is of white color. The black plate’s sinks deeper into the snow because:
A. The black plate reflects light better.
B. The white plate reflects light better.
C. The black plate radiates heat better.
D. The white plate radiates heat better.
E. Both of the plates reflect light and radiate heat at the same rate.

Answer 1

In the solution we will use the concept of the radiation of heat from the black color plate and white color plate and also use the concept of good absorber and good emitter.

Complete step by step answer:
Given:
Two identical plates are placed on the top of a snow bank on a sunny day.
According to Kirchhoff’s law of heat radiation, black body is a good absorber and also a good emitter compared to white body. The absorptivity and emissivity of black body is higher than the white body. So the black plate is a good absorber and a good emitter of heat radiation compared to white plates which are installed on the top of the snow bank. The black plate will absorb more heat and also emit more heat compared to white plate so that the temperature of the black plate will be higher than the white plate. As a result the melting of snow below the black plate is more compared to the snow below the white plate so the black plates will sink deeper into the snow compared to white plate.
Therefore, the option (C) is the correct answer that is, the black plate radiates heat better.

Note: For this type of question remember one concept that the black body is a good emitter as well as a good absorber compared to other bodies. The emissivity and absorptivity of black body is of higher value compared to other bodies. The reflectivity of white body is equal to one.