Question

Answer in brief:

What is a perfect blackbody? How can it be realized in practice?

Answer 1

1. A perfect blackbody, also known as a blackbody, is a body that absorbs all of the radiant energy that is incident on it.
2. Fery created a spherical blackbody, which consists of a double-walled hollow sphere having a tiny hole or aperture, through which radiant heat can enter, as shown in Figure. The sphere's inside wall is blackened with lampblack, while the outside is silver plated. To reduce heat loss through conduction and convection, the space between the two walls is evacuated.
3. Any radiation entering the sphere through the aperture is reflected several times, with around 97% of it being absorbed by the lampblack covering at each incidence.
4. After a series of internal reflections, the radiation is almost fully absorbed. The probability of incident radiation escaping out is reduced by a conical projection on the inside wall opposite the opening.

Ferry’s blackbody

1. When the sphere is placed in a bath of appropriate fused salts to maintain the desired temperature, the hole acts as a source of black-body radiation. The intensity and nature of the radiation are solely determined by the temperature of the walls.
2. A blackbody has a coefficient of absorption of one by definition. As a result, its coefficients of reflection and transmission are both zero.
3. The radiation emitted by a blackbody, known as blackbody radiation, covers the complete electromagnetic spectrum. As a result, a blackbody is also known as a full radiator.