Biomedical Engineering Reference
In-Depth Information
t
⎛
⎞
⎠
−
F
1
⎝
′
A
2
H
=
F
e
⎛
⎝
0.010 m
(
⎞
⎠
−
+
20.80 D)
1.52
′
A
2
H
=
(100 cm/m)
+
14.82 D
′
A
2
H
= −
0.92 cm
Calculation of F
n
and F
v
We can calculate
F
n
and
F
v
using the thick lens formulae:
F
2
F
n
=
+
F
1
1
−
cF
2
−
6.93 D
F
n
=
+
20.80 D
⎛
⎝
0.010 m
1.52
⎞
⎠
(
−
6.93 D)
1
−
F
n
= +
14.17 D
F
1
F
v
=
+
F
2
1
−
cF
1
+
20.80
F
v
=
+
(
−
6.93 D)
⎛
⎝
0.010 m
⎞
⎠
1
−
(
+
20.80 D)
1.52
F
v
= +
17.17 D
(b) In treating the lens as an equivalent lens, distances are measured from the
principal planes. As in the case of a thin lens, we ignore the lens's index of
refraction. If the object is located 15.00 cm from the front surface of the
lens, then it is located 14.69 cm (i.e., 15.00
−
0.31 cm
=
14.69 cm) in front
of the primary principal plane. Substituting, we have:
′
=
L
L
+
F
e
(100)(1.00)
−
⎡
⎥
⎤
⎥
′
=
L
+
14.82 D
14.69 cm
′
=
−
L
6.81 D
+
14.82 D
L
′
=
+
8.01 D
n
′
′
=
L
′
l
(100)(1.00)
l
′
=
+
8.01 D
′
=
+
l
12.48 cm
