# 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.

**Q2: **

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?

- A
- B
- C
- D
- E

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?

**Q3: **

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 cm^{3}
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/m^{3}.

How many photons were required to vaporize the flesh?

- A
- B
- C
- D
- E

What was the minimum power output during the flash?

**Q11: **

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.