Department of Natural Sciences

Clayton College & State University

November 18, 2003

Physics 1112 – Quiz 10

Name _______SOLUTION______________________________

1. A boy 1.40 m tall stands 3.00 m from a reflecting globe in a garden. The diameter of the globe is 3.20 m. (Hint: A convex mirror has a negative focal length.)

a. Where is the image of the person relative to the surface of the globe?

f = (-3.20 m)/4 = -0.800 m p = + 3.00 m

1/p + 1/q = 1/f

1/q = 1/f - 1/p

1/q = 1/(-0.800 m) –1/(3.00 m) = -0.0158 m^-1

q = -0.632 m or 63.2 cm behind the globe.

b. What is the magnification of the image?

M = -q/p

M = -(-0.632 m)/(3.00 m) = 0.211

c. Draw a ray diagram and check the numbers you obtained in a and b.

d. Describe the mouse’s image (real or virtual, upright or inverted, enlarged or reduced?)

Virtual (q < 0)

Upright (M > 0)

Reduced (M < 1)