Phys 375 HW 3
Fall 2006
Due 2 / 4 October, 2006
1. Imagine that you are standing 5 feet from, and looking directly toward, a brass ball 1
foot in diameter hanging in front of a pawn shop. State the type of image, position,
magnification, and whether it is upright or inverted.
2. Design a little dentist’s mirror to be fixed at the end of a shaft for use in the mouth of
some happy soul. The requirements are (1) that the image be erect as seen by the dentist
and (2) and that when held 1.5 cm from a tooth the mirror produces and image twice life-
size.
3. A candle that is 6.00 cm tall is standing 10 cm from a thin diverging lens whose focal
length is -30 cm. Determine the location of the image and state the type of image,
magnification, and whether it is upright or inverted.
4. Compute the image location and magnification of an object 30 cm from the front lens
of the thin lens combination shown in the figure. Do the calculation by finding the effect
of each lens separately and make a sketch of the appropriate rays.
10 cm
f
1
=+30 cm f
2
=-20 cm
object
5. Using geometry and the diagram below left, calculate the focal length of the mirror in
terms of a, b, and L for two cases: a) screen outside the focal length (as shown in the
diagram), b) screen inside the focal length (not shown, so create a new sketch).
mirror
screen
a
b
L
mirror
screen
a
b
L
lens
h
1
xL
h
2
6. Using geometry and the diagram above right, find the focal length of the diverging
lens in terms of h1, h2, L and x.