Phys 375 HW 3
Fall 2009
Due 5 / 6 October, 2009
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.
Use the mirror equation 1/s
o
+1/s
i
= 2/R, with R = 0.5 ft. The sign convention for
radius is negative here.
1/s
i
= 2/(0.5ft)1/(5ft) so s
i
= 5/21 = 0.24 ft. M = s
i
/s
o
= (
0.24)/5 = 0.048. The image is virtual, erect, and 0.048 times the object size.
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.
The mirror must be concave to produce an upright, virtual image. M = 2.0 =
s
i
/0.015 m implies s
i
= 0.03 m. Putting into the mirror equation gives 1/f = 1/0.015
1/0.03 so f = 0.03 m and R = 0.06 m.
3.
A candle that is 6.00 cm tall is standing 10 cm from a thin diverging lens whose focal
length is 30 cm.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '11
 ENO
 Physics

Click to edit the document details