Spring 2005

MWF 11:30

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

# REVIEW QUESTIONS OF Home Work 18

# 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.

#

# EXCERISES OF Home Work 18

## 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. **