PHYS 135B Homework Set 10
Dr. Zorba
1-) (a) How hot is a metal being welded if it radiates most strongly at 440
nm? (b) What is the temperature if the peak of a blackbody spectrum is at
25.0 nm? (c) What is the wavelength at the peak of a blackbody spectr u m i f
the body is at a temperature of 2800 K?
2-) An HCl molecule vibrates with a natural frequency of 8.1x 1013 Hz.
What is the difference in energy (in joules and electron volts) between
possible values of the oscillation energy?
3-) Estimate the peak wavelength for radiations from (a) ice at 0º C,
(b) a floodlamp at 3300 K, (c) helium at 4 K, assuming blackbody emission.
(d) What region of the electromagnetic spectrum is each?
4-) (a) What is the energy range in eV, of photons in the visible spectrum, of
wavelength 400 nm to 750 nm?
(b) What color of light carries more energy, blue or red? Explain why?
5-) In a photoelectric-effect experiment it is observed that no current flows
unless the wavelength is less than 570 nm. (a) What is the work function of
this material? (b) What is the stopping potential required if light of
wavelength 400 nm is used?