# Worksheet: Thermal Radiation

In this worksheet, we will practice determining the relationship between the temperature of an object and the power and peak wavelength of radiation it emits.

**Q1: **

The surface of a desert has an average temperature of 315 K
and an emissivity of 0.45.
Determine the power of the infrared radiation emitted per square meter of the surface.
Use a value of W/m^{2}⋅K^{4}
for the Stefan–Boltzmann constant.
Answer to three significant figures.

**Q2: **

An object emits infrared radiation. The emitting surface
area of the object is
0.25 m^{2} and its
temperature is 350 K. The
emitting surface has an emissivity of 0.75. Find the power of the emitted
radiation. Use a value of
W/m^{2}⋅K^{4}
for the Stefan–Boltzmann constant. Answer to
three significant figures.

**Q3: **

An object that is an ideal blackbody radiator emits electromagnetic
radiation at many wavelengths, the most powerfully emitted of which is m. The surface area of the object is 0.15 m^{2}. Find the total power
of the emitted radiation. Use a value of m⋅K for
Wien’s constant. Use a value of W/m^{2}⋅K^{4}
for the Stefan–Boltzmann constant. Answer to three significant figures.

**Q4: **

An object that is an ideal blackbody radiator emits electromagnetic radiation at many wavelengths. The wavelength of electromagnetic radiation that is emitted with the greatest power is 1.25 μm. Find the temperature of the object to three significant figures. Use a value of m⋅K for Wien’s constant.

**Q5: **

A surface with an area of 0.15 m^{2} emits infrared radiation with a power of
220 W.
The emitting surface has an emissivity of 0.65. Find the temperature of the surface.
Use a value of W/m^{2}⋅K^{4}
for the Stefan–Boltzmann constant. Give your answer to three significant figures.

**Q6: **

An object that is an ideal blackbody radiator emits electromagnetic
radiation at many wavelengths. The total power emitted is 750 W. The surface
area of the object is 1.25 m^{2}. Find the wavelength that is emitted
with the greatest power. Use a value of m⋅K for
Wien’s constant. Use a value of W/m^{2}⋅K^{4}
for the Stefan–Boltzmann constant. Answer to three significant figures.

- A m
- B m
- C m
- D m
- E m

**Q7: **

The graph shows the change in the power of the infrared radiation emitted per square meter of two surfaces. Which curve color represents the surface with the higher emissivity?

- ABlue
- BPurple

**Q8: **

An object that is an ideal blackbody radiator is at a temperature of 325 K. The object emits the electromagnetic radiation spectrum shown in the diagram. Find the value of the wavelength that is emitted with greatest intensity. Use a value of m⋅K for Wien’s constant. Answer to three significant figures.

- A m
- B m
- C m
- D m
- E m