Case 1 on page 410 of your text (The color of the sky…). Do all parts a, b, c, d, and e.
Your eye is similar to a camera. Why does squinting your eye increase the depth of field and make it easier to focus? To help answer this, try the following experiment, with your glasses or contacts removed. (If you have perfect vision, you will have to get a friend who needs corrective lenses to try it.) Make a very small hole in a piece of paper--about the size of a pencil lead. Does looking through this hole make things appear more in focus? Is there any disadvantage?
Exercise 19 on page 435 (A CD or DVD could store much more music…)