Summary

• Young's interference
• Dispersion
• Diffraction

• Class quiz
  
• Thin film interference
  • thin film diagram
  • microscope slides
  • soap bubbles
    
    Example #1
    
    Example #2
    
  
  
  
  
• Polarization of light
  • by polaroid sheets applet
  • by reflection
  • by scattering
    Example #3
    
  • liquid crystal displays
  • crossed polarizers
  
  

gc6 tb24.34
Compare a 4000 lines/cm diffraction grating with a 6000 lines/cm grating.
A. The 4000 lines/cm grating produces greater dispersion.
B. The 6000 lines/cm grating produces greater dispersion.
C. The dispersions are equal but orders are sharper with 4000 lines/cm grating.
D. The dispersions are equal but orders are sharper with 6000 lines/cm grating.
Answer







kw4
Why don't we notice interference patterns when we turn on two lights in a room?
  A. The lights aren't in phase.
  B. The lights are too bright.
  C. The lights are too dim.
  D. The air molecules disturb the interference pattern.
Answer







gc6 24.76
How thick should an antireflection coating (n = 1.38) on glass (n = 1.55) be in order to suppress reflection of λ = 515 nm light?
A. 93.3 nm            B. 129 nm
C. 187 nm              D. 258 nm
Answer







gc6 24.57
At what angle should the axes of two ideal Polaroids be placed in order to reduce the intensity of incident unpolarized light by a factor of 10?
A. 84.3°            B. 71.6°
C. 78.5°            D. 63.4°
Answer







 



B. The 6000 lines/cm grating produces greater dispersion.
The angular separation between wavelengths is proportional to the wavelength divided by the separation d between adjacent lines. Therefore the smaller d produces the larger dispersion.












 



A. The lights aren't in phase.
In order to see constructive and destructive interference, there must be a fixed phase relationship between the waves coming from various sources. There is no such relationship for light waves emitted from two different light bulbs. The light bulbs also emit many different wavelengths simultaneously, further complicating efforts to detect wave interference.












 



A. 93.3 nm













 



D. 63.4°