# 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.

Q1:

Determine the power intensity of radiation per unit wavelength emitted at a wavelength of 500.0 nm by a blackbody at a temperature of 10,000 K.

• A W/m3
• B W/m3
• C W/m3
• D W/m3
• E W/m3

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 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?

• A
• B
• C
• D
• E

What was the minimum power output during the flash?

Q4:

A photon has the same energy as a proton that is moving at .

What is the wavelength of the photon?

What is the energy of the photon?

What is the kinetic energy of the proton?

Q5:

What is the minimum frequency of a photon required to ionize a ion in its first excited state if the energy required is 30.6 eV? Use a value of eV⋅s for the value of the Planck constant.

• A Hz
• B Hz
• C Hz
• D Hz
• E Hz

Q6:

The tungsten elements of incandescent light bulbs operate at 700 K. At what frequency does the filament radiate maximum energy?

• A Hz
• B Hz
• C Hz
• D Hz
• E Hz

Q7:

The radiant energy from the Sun reaches its maximum at a wavelength of about 0.5 μm. What is the approximate temperature of the Sun’s surface?

Q8:

The wavelengths of visible light range from approximately 390 nm to 770 nm. What is the corresponding range of photon energies for visible light?

• A J to J
• B J to J
• C J to J
• D J to J
• E J to J

Q9:

Calculate the temperature of the Sun, modeling the Sun as a black body emitting radiation at a maximum intensity at a wavelength of 0.500 micrometers.

Q10:

Calculate the heat flux emitted from the Sun’s surface, modeling the Sun as a black body emitting radiation at maximum intensity at a 0.50-micrometer wavelength.

• A kW/m2
• B kW/m2
• C kW/m2
• D kW/m2
• E kW/m2

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.

Q12:

Treating the human body as a blackbody, determine the percentage increase in the total power of its radiation when its temperature increases from to .

• A0.683%
• B0.863%
• C4.82%
• D0.858%
• E4.95%

Q13:

The tungsten elements of incandescent light bulbs operate at 700 K. At what frequency does the filament radiate the most energy?

• A Hz
• B Hz
• C Hz
• D Hz
• E Hz

Q14:

What voltage must be applied to an X-ray tube to obtain an X-ray with a wavelength of 0.100 nm?