Summary

• Relativistic mechanics

• Blackbody radiation applet
  • experiment
  • Planck's theory
  • quantized energy
    Example #1
    
    Example #2
    
  
  
  
  
  
• The photoelectric effect applet
  • experiment another applet
    • the cutoff frequency
    • KE_max and intensity
    • KE_max and frequency
    • instant photoelectrons
  • Einstein's theory
  • quantized light
    Example #3
    
    Example #4
    
    Example #5
    
  • wave-particle duality info & graphs
  
  

kw4 22.q.34
Stars emit light according to their temperatures. Which star would be the hottest?
   A. red           B. yellow
   C. white       D. blue
Answer







gc6 27.9
What is the peak wavelength of the EM radiation issuing from the pupil of the human eye, assuming an eye temperature of 37°C?
A. 9.35 µm               B. 2.90 µm
C. 1068 nm               D. 78.4 µm
Answer







kw5
Light striking a clean metal produces photoelectrons. If the light is made twice as bright, what happens to the average kinetic energy of the photoelectrons?
A. The energy doubles.
B. The energy stays the same.
C. The energy is cut in half.
D. It's impossible to say.
Answer







kw5
Blue light shines on a metal, producing photoelectrons. When a red light is used the maximum KE of the photoelectrons
A. increases.
B. decreases.
C. stays the same.
D. Depends on the light intensity.
Answer







sj6 40.14
For a certain surface the emitted photoelectrons have v_max=460 km/s when l=625 nm. What minimum wavelength produces photoelectrons?
A. 756 nm               B. 897 nm
C. 962 nm               D. 1064 nm
Answer







 



D. blue
The bluer the light, the hotter the object! An object that glows blue or bluish-white is hotter than an object that glows white.












 



A. 9.35 µm













 



B. The energy stays the same.
The average kinetic energy of the emitted photoelectrons depends only upon the frequency of the light. Making the light brighter produces more photoelectrons, but they have the same energy distribution as before.












 



B. decreases.
Red light is composed of photons that have a lower frequency and thus less energy than blue photons. The emitted photoelectrons will therefore have less energy when red light is used.












 



B. 897 nm