A pinhole is made in a hollow sphere of radius `5cm` whose inner wall is at temperature `727^(@)C`. Find the power radiated per unit area.
[Stefan's constant `sigma=5.7xx10^(-8)J//m^(2)sK^(4)`, emissivity `(e)=0.2`]

A small hole is made in a hollow sphere whose walls are at 723^(@)C . Find the total energy radiated per seond per cm^(2) . Given Stenfan's constant = 5.7 xx 10^(-5) erg cm^(-2) s^(-1) K^(-4) .

A body having a surface area of 50cm^2 radiates 300J of energy per minute at a temperature of 727^(@)C . The emissivity of the body is ( Stefan's constant =5.67xx10^(-8)W//m^2K^4 )

A spherical black body of 5 cm radius is maintained at a temperature of 327^(@)C . Then the power radiated will be (sigma=5.7xx10^(-8)"SI unit")

A thin square steel plate with each side equal to 10 cm is heated by a blacksmith. The rate of radiated energy by the heated plate is 1134 W . The temperature of the hot steel plate is (Stefan's constant sigma = 5.67 xx10^(-8) " watt "m^(-2) K^(-4) , emissivity of the plate = 1)

The value of Stefan's constant is sigma =5.76xx 10^(-8) J s^(-1) m^(-2)K^(-4). Find its value in cgs system.

A metallic sphere having radius 0.08 m and mass m = 10 kg is heated to a temperature of 227^(@)C and suspended inside a box whose walls ae at a temperature of 27^(@)C . The maximum rate at which its temperature will fall is:- (Take e =1 , Stefan's constant sigma = 5.8 xx 10^(-8) W//m^(-2)K^(-4) and specific heat of the metal s = 90 cal//kg//deg J = 4.2 "Joules"//"Calorie")

The surface area of a black body is 5xx10^(-4) m^(2) and its temperature is 727^@C . Energy radiated by it per minute is (Take sigma =5.67xx10^(-8) "J m"^(-2) s^(-1) K^(-4) )

Calculate the amount of heat radiated per second by a body of surface are 10 cm^(2) kept in thermal equilibrium in a roomat temperature 27^(@)C . The emissivity of the surface = 0.80 and Stefan's constant sigma ~= 6 xx 10^(-8) W//m^(2) K^(4)

Calculate the maximum amount of heat which may be lost per second by radiation by a sphere 14cm in diameter at a temperature of 227^(@)C , when placed in an enclosure at 27^(@)C . Given Stefan's constant = 5.7 xx 10^(-8)Wm^(-2)K^(-4) .