1. In the American midwest, rural roads are laid out in a square grid one mile on a side. A passenger on an eastbound airliner braces his head against a window frame and observes that one of these grid roads passes the edge of the window every six seconds. How fast is the airplane traveling relative to the ground?

2. The preceding problem used the relationship v = . If the wavelength of the repeating road pattern is 1 mile, what is the frequency in roads per second? Show that v = leads to the answer of Problem 1.

3. Chlorophyll in green plants absorbs light especially well at wavelengths around 6600 . What color is this light? What is the frequency of the light? (1 cm = 10 )

4. What is the energy in ergs of one photon of light of wavelength 6600 ? (Planck's Constant is h = 6.626 X 10 erg sec.) What is the energy in ergs of one mole of these photons?