Question

A polished metal plate with a rough black spot on it is heated to about $1400{\text{ K}}$ and quickly taken into a dark room. Which one of the following statements will be correct?
A. The spot will appear brighter than the plate
B. The spot will appear darker than the plate
C. The spot and the plate will appear equally bright
D. The spot and the plate will not be visible in the dark room

Answer 1

Hint: As it is given that, a polished metal plate with rough black spot on it is heated to about $1400{\text{ K}}$ and quickly taken into a dark room.

Complete step by step solution:
We have studied in thermodynamics the Kirchhoff law states the good absorbers are good emitters. Since the given metal plate is a rough black spot. So it is good absorbers and also it is good emitters. Also we know that the black body almost completely absorbs the heat and light and the material gets warm and the particles of the material begin to accelerate. and emits radiation when they absorb more intense heat When a metal body is heated to $1400{\text{ K}}$, it absorbs a lot of radiation. After heating and taken into a dark room, it begins to emit these radiations, hence the spot appears brighter in the dark room.

Hence the correct option is (A).

Note: This is a theoretical question, so explanation of this question is on the memory based and be careful during explanation that it absorbs a radiation at $1400{\text{ K}}$ when it is heated and taken into a dark room.