Question

A piece of blue glass heated to a high temperature and a piece of red glass at room temperature, are taken inside a dimly lit room, then
A. The blue glass will look blue and red will look as usual
B. Red looks brighter red and blue looks ordinary blue
C. Blue shines like brighter red compared to the red piece
D. Both the pieces will look equally red

Answer 1

Hint: A body radiates electromagnetic radiation at all temperatures. When temperature of a material is increased, it starts absorbing radiations of higher wavelengths incident on it except the lower wavelengths are reflected.

Complete step-by-step answer:
The electromagnetic spectrum consists of gamma rays, x-rays, ultraviolet rays, visible rays, infrared rays, microwaves and radio waves in the order of increasing wavelength and decreasing frequency.
A body radiates electromagnetic radiation. The molecules of material are capable of absorbing, emitting and reflecting radiation. The rate of emission of radiation increases with temperature.
When a piece of blue glass is heated to a high temperature, then the absorption of radiation by the glass increases. This means that it starts to absorb the higher wavelengths of electromagnetic radiation going towards the infrared region which has a high wavelength. But it reflects the blue light which has lower wavelength.
When this blue glass is taken to a dimly lit room, it will appear bright blue in colour compared to a red glass at high temperature. So, the correct answer is option C.

Note: The colour of a material is an intrinsic property of a material. It is a wavelength which the material reflects while it absorbs all other wavelengths of the radiation incident on it. The reflected wavelength decides the colour of the material. It can change with temperature only if there is change in structure of molecules which is possible at very high temperatures in case of glass. So we consider the temperature of blue glass not too high here so it reflects the blue wavelength.