Optical Instruments
341
Problem Solutions
25.1
Using the thin lens equation, the image distance is
( )( )
150 cm
25.0 cm
30.0 cm
150 cm
25.0 cm
pf
q
pf
==
=
−−
so the image is located
30.0 cm beyond the lens . The lateral magnification is
30.0 cm
1
150 cm
5
q
M
p
=−
= −
25.2
The
f
number of a camera lens is defined as
number
focal length diameter
f
=
.
Therefore, the diameter is
55 mm
31 mm
number
1.8
f
D
f
=
25.3
The thin lens equation,
111
p
qf
+=
, gives the image distance as
( )( )
3
100 m
52.0 mm
52.0 mm
100 m
52.0
10
m
pf
q
−
=
×
From the magnitude of the lateral magnification,
M hh
qp
′
−
, where the height of
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 Spring '09
 Physics, Work, optical instruments, 1.09 mm

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