Perfectly Black Body

Black body at a temperature of 1640K has the wavelength corresponding to maximum emission equal to 1.75mu m Assuming the moon to be a perfectly black body the temperature of the moon if the wavelength corresponding to maximum emission is 14.35mum is .

A highly conducting solid sphere of radius R density rho and specific heat s is kept in an evacuted chamber. A parallel beam of thermal radiation of instensity I is incident on its surfcae Consider the sphere to be a perfectly black body and its temperature at certain instant considered at t =0 is T_(0) [Take Stefan's constant as sigma ] Answer the following questions based on above information The equation which gives the temperature T of the sphere as a function of time is .

A highly conducting solid sphere of radius R density rho and specific heat s is kept in an evacuted chamber. A parallel beam of thermal radiation of instensity I is incident on its surfcae Consider the sphere to be a perfectly black body and its temperature at certain instant considered at t =0 is T_(0) [Take Stefan's constant as sigma ] Answer the following questions based on above information The maximum attainable temperature of the sphere is .

A and B are two isolated spheres kept in close proximity so that they can exchange energy by radiation as shown in the following figure. The two spheres ,have identical physical dimension, but the surface of A behaves like a perfectly black body while the surface of B reflects 20% of all the radiations it receives. They are isolated from all other sources of radiation.

Two stars A and B of radius 2R and R respectively radiates power like perfectly black body in the ratio 1:4 .Their peak wavelengths (corresponding to maximum spectral power) differs by 150nm .Sum of their temperatures on surface is 500 alpha K . Find alpha .Given, Wien's constant b=3times10^(6)K-nm

Is it neccesary that all black coloured bodies to be regarded as perfectly black bodies ?