1. You stand one meter away from a plane mirror. How far is it from you to your image?

ans: 2.0 m; the image is the same distance behind the mirror as you are in front.

2. An object is at a distance of 30 cm from a thin convex lens, along its axis. The lens has a focal length of 10 cm. What are the values, respectively, of the image distance and magnification?

ans: 15 cm and -0.50; use geometry or 1/q = 1/f - 1/p, and M = -q/p.

3. A projector lens is needed to form an image on a screen 10 times the size of its corresponding object. The screen is located 8 m from the lens. What is the required focal length of the lens?

ans: 0.73 m; two steps- use M = -q/p to get p (p, q will be positive and M=-10), and then 1/f = 1/p + 1/q.

4. What is the image location of an object 1 m in front of a converging lens of focal length 20 cm?

ans: q = +25.0 cm; use geometry or 1/q = 1/f - 1/p. Don't forget to convert 1 m to 100 cm!

5. A magnifying glass has a convex lens of focal length 15 cm. At what distance from a postage stamp should you hold this lens to get a magnification of +2?

ans: 7.5 cm; use geometry or M = -q/p.