Heating a blackbody of fixed area increases its total emitted power and moves the peak of its power-per-unit-wavelength spectrum to shorter wavelengths.

Which statement defines an ideal blackbody?

• It absorbs all incident radiation at every wavelength
• It absorbs visible light but reflects every infrared wavelength
• It emits no radiation even when its temperature is above zero kelvin

What is the ultraviolet catastrophe in the classical Rayleigh-Jeans model?

• A predicted absence of radiation throughout the ultraviolet band
• A short-wavelength divergence giving infinite total emitted power
• A predicted sharp ultraviolet line replacing the broad thermal spectrum

A star is approximately a blackbody. Its power-per-unit-wavelength spectrum peaks at 560 nm. What can Wien's law estimate from that peak alone?

• An estimate of its surface temperature
• An estimate of its distance from Earth
• An estimate of its age since formation

Which change in Planck's oscillator model removes the short-wavelength divergence?

• Every frequency receives equal energy regardless of its quantum size
• Oscillator energy changes occur in discrete multiples of hf
• All short-wavelength radiation is forbidden at every temperature

How does a blackbody's total emitted power per unit area depend on its temperature T in kelvin?

• It is proportional to the fourth power, T^4
• It is proportional to the reciprocal temperature, 1/T
• It is proportional to temperature measured in degrees Celsius

Blackbody A's power-per-unit-wavelength spectrum peaks at 800 nm. Blackbody B's peaks at 400 nm. How do their kelvin temperatures compare?

• A has twice B's temperature because its peak wavelength is twice as long
• A and B have equal temperatures because both spectra contain many wavelengths
• B has twice A's temperature because its peak wavelength is half as long

A blackbody's power-per-unit-wavelength spectrum peaks at 966 nm. Use b = 2.898 x 10^-3 m K and Wien's law. What is its temperature in kelvin?