# Worksheet: Thermal Radiation

Q1:

The intensity of the radiation of sunlight at a distance from the Sun of km is measured to be W/m2.

Calculate the radiative power of the Sun.

• A W
• B W
• C W
• D W
• E W

Calculate the radius of the Sun. Use a value of K for the Sun’s temperature and use a value of 1.0 for the Sun’s emissivity.

• A km
• B km
• C km
• D km
• E km

Q2:

A 100-meter-long pipe is at a temperature of . Find the heat loss due from the pipe due to radiation if the pipe’s outer diameter is 10 cm. The surface emissivity of the pipe is 0.7.

Q3:

An infrared heater for a sauna has a surface area of 0.050 m2 and an emissivity of 0.84. What temperature must it run at if the required power is 360 W? Neglect the temperature of the environment.

Q4:

What are three major modes of heat transfer?

• AConvection, isobaric, and radiation.
• BRadiation, friction, and convection.
• CConduction, isothermal, and isentropic.
• DConduction, convection, and radiation.

Q5:

Calculate heat loss per meter length due to radiation of a metal pipe with an emissivity of 0.930. The temperature of the outer surface of the pipe is 311 K. The outer diameter of the pipe is 15.24 cm.

Q6:

Heat loss due to radiation for a pipe is 80.0 kW. The pipe is 100.0 m long and its outer radius is 10.0 cm. The surface emissivity of the pipe is 0.70. Find the temperature of the pipe.

Q7:

Thermal radiation from the Sun has an intensity of about 600 W/m2 at the radius of Mars’s orbit. Assume the Sun is a perfect sphere and its temperature is uniform. Ignore any greenhouse effects.

Assuming the Sun’s rays are parallel, Find the area that must be multiplied by to get the total radiation intercepted by Mars. Use a value of km for the radius of Mars.

• A
• B
• C
• D
• E

Find the temperature at which Mars radiates energy at the same rate. Assume that at the infrared wavelengths where it radiates, the emissivity e is 1.00.