Perfect Black Body

An electromagnetic plane wave of intensity $I=0.20 \mathrm{W} {\mathrm{cm}}^{-2}$ falls on a plane mirror surface with reflection co-efficient $0.8$. In terms of the photon theory, the magnitude of pressure exerted by light on that surface is $n_1\times {10}^{-n_2} \mathrm{N} {\mathrm{cm}}^{-2}$. Calculate $n_1{n}_2$ product.
When expressed in scientific notation.

A cavity with walls made of any material, with a small opening, is an excellent black body. This is called Ferry's black body.

The working of ferry's black body depends on the principle of :

The opening kept in hollow sphere for construction of Ferry's black body is termed as :

What is Ferry's black body?

What is perfectly black body? How can it be realized in practice?

A good absorber is

There is a rough black spot on a polished metallic plate. If the plate is heated up to $1400 \mathrm{K}$ (approximately) and then at once taken in a dark room, then

In rainy season, on a clear night the black seat of a bicycle becomes wet because

The surface of a black body is at a temperature ${727}^{ \mathrm{o}}\mathrm{C}$ and its cross section is $1\mathrm{ }{\mathrm{m}}^2$ . Heat radiated from this surface in one minute in joules is (Stefan's constant $5.7\times {10}^{-8} \mathrm{W} {\mathrm{m}}^{-2} {\mathrm{K}}^{-4}$ )

An ideal black body at room temperature is thrown in a furnance. It is observed that

Assertion: For higher temperature, the peak emission wavelength of a black body shifts to lower wavelength.

Reason: Peak emission wavelengths of a black body is inversely proportional to absolute temperature.

Assertion: The emissive power of a blackbody is minimum at any given temperature compared to another body of the same shape and size.

Reason: Blackbodies are very good absorbers.

Assertion: All black colour objects are considered as black bodies.

Reason: Black colour is good absorber of heat.

Assertion: For a perfectly black body, absorption coefficient and emission coefficient, each is one.

Reason: Perfect absorbers are perfect emitters.

Assertion: A perfectly black coloured body must acts as black body.

Reason: A perfectly black coloured body absorbs all light falling on it.

Temperature of a black body increases from $327{ }^{\mathrm{o}}\mathrm{C} \text{to} 927{ }^{\mathrm{o}}\mathrm{C}$, the initial energy possessed is $2 \mathrm{kJ}$, what is its final energy

The temperature at which a black body ceases to radiate energy, is

An ideal black body, at room temperature, is thrown into a furnance. It is observed that,

A perfect black body is one whose emissive power is