Worksheet: Blackbody Radiation and Photon Energy
In this worksheet, we will practice relating a blackbody temperature to its emitted and absorbed light wavelengths and how to relate those to photon energies.
A 200 W heater emits a 1.50 μm radiation. Radiation from the heater warms a body of mass 4.00 kg by 2.00 K.
What value of the energy quantum does it emit?
Assuming that the specific heat capacity of the body is 0.83 kcal/kg⋅K, how many photons must be absorbed to warm the body?
Assuming that all the radiation that the heater emits is absorbed by the body, how much time is required for the body’s temperature to increase?
Lasers can be used as surgical instruments to vaporize flesh by heating it. A carbon dioxide laser used in surgery emits infrared radiation with a wavelength of 10.6 μm. In 1.00 ms, this laser raised the temperature of 1.00 cm3 of flesh from to . Flesh has a latent heat of vaporization of 2,256 kJ/kg. Considering the human flesh as water, the specific heat is and the density is 997 kg/m3.
How many photons were required to vaporize the flesh?
What was the minimum power output during the flash?
In about five billion years, the Sun will evolve into a red giant. Assume that its surface temperature will decrease to about half its present value of 5,778 K, while its present radius of m will increase to m, which is the current Earth-Sun distance. Calculate the ratio of the total power emitted by the Sun in its red giant stage to its present power.