Thermal Radiation

Two metal spheres have radii rand 2r and they emit thermal radiation with maximum intensities at wavelengths lambda and 2lambda . respectively. The respective ratio of the radiant energy emitted by them per second will be

A heated body maitained at T K emits thermal radiation of total energy E with a maximum intensity at frequency v. The emissivity of the material is 0.5. If the temperature of the body be increased and maintained at temperature 3T K, then :- (i) The maximum intensity of the emitted radiation will occur at frequency v/3 (ii) The maximum intensity of the emitted radiation will occur at frequency 3v. (iii) The total energy of emitted radiation will become 81 E (iv) The total energy of emitted radiation will become 27 E

Unlike most other plants, a special type of cabbage called skunk cabbage can regulate its internal temperature ( set at T = 22^(@)C )by altering the rate at which it produces energy. If it becomes covered with snow, it can increase that its thermal radiation metls the snow in order to re-expose the plant to sunlight. Let's model a skunk cabbage with a cylinder of height h = 5.0 cm and radius R = 1.5 cm and assume it is surrounded by a snow wall at temperature T_("env") = - 3.0^(@)C (Figure) . If the emissivity epsilon is 0.80, what is the net rate of energy exchange via thermal radiation between the plant's curved side and the snow ?

An electric heater ofpower 1kW emits thermal radiations the surface area of heating element of heater is 200 cm^(2) . If this heating element is treated like a black bodyfind the temperature at its surface. Assume its temperature is very much higher then its surroundings.

A sphere of radius 0.350m, temperature 27.0^(@)C , and emissivity 0.850 is located in an environment of temperature 77.0^(@)C . At what rate does the sphere (a) emit and (b) absorb thermal radiation ? (c ) What is the sphere's net change in energy in 3.50 min ?