1. The focal length of a concave mirror is 20 cm. What is its radius of curvature? (in cm)

2. If for a concave mirror the object and image distances are both 12 cm, what is the mirror's focal length? (in cm)

3. The index of refraction for water is 1.33, and for flint glass it is 1.66. When a beam of light traveling in flint glass is reflected at a surface of water, the phase change of the reflected beam is a) 90 degrees. b) 60 degrees. c) 0 degrees. d) 180 degrees. e) 45 degrees.

4. Light of wavelength 370 nm is reflected constructively from a thin layer of oil (index of refraction 1.5) which rests on top of water (index of refraction 1.33). What is the minimum thickness of the oil layer? (in nm)

5. What is the minimal thickness of an antireflective coating consisting of a thin layer of magnesium fluoride (index of refraction n=1.38) on the surface of glass (index of refraction n=1.5)? You would like your coating to eliminate reflections of green light with a wavelength of 510 nm. (in nm)

6. In Young's two-slit experiment the separation between the two slits is 2.5 times larger than the wavelength of the light. At what angle (in degrees) above the central bright fringe is the first bright fringe located?

7. The circuit in the figure has two identical resistors and three identical inductors. If L = 70 mH, what value must R have to give a time constant of 50 ?s?