The Physical World I

Spring 2005
MWF 11:30

Instructor: Dr. Bruce Law, CW 327, Tel: 532-1618.


R29.3. For a small opening.

R29.4. For a given opening diffraction is more pronounced for longer wavelengths.

R29.6. Interference occurs for all types of waves.

R29.12. The spectrum of colors seen in gasoline splotches origins from interference between light reflected from the front and back surface of the gasoline film. For a dry street there is only one reflected beam (and not two) therefore you cannot see this interference effect.



E29.2. Sound waves have a wavelength of order 1 meter and are therefore readily diffracted (i.e. bent) by objects of that size (eg. doors, people, etc). By contrast, light which has a wavelength of order 0.0000005 meters is not readily diffracted by large everyday objects, i.e. light generally travels in a straight line through doorways and windows.

E29.3. Same reasoning as in E29.2 above but where the wavelength of radio waves is of order of many meters.

E29.10. Red light has a longer wavelength than blue light therefore the interference pattern will be more spread out for the red light than the blue light. (Recall that in this case you must think about the extra distance one wave (from one slit) must travel relative to the other wave (which passes through the other slit). This extra distance must be a multiple of the wavelength, hence, for longer wavelengths the interference pattern is spread out more.