Biomedical Engineering Reference
In-Depth Information
2. (a) Calculate powers of two surfaces:
(
n
−
n
)
′
F
1
=
r
1
(1.52
−
1.00)
F
1
=
+
0.025 m
F
1
=
+
20.80 D
(
n
−
n
)
′
F
2
=
r
2
(1.00
−
1.52)
F
2
=
+
0.075 m
F
2
=
−
6.93 D
Equivalent power
:
t
⎛
⎞
⎠
F
e
=
F
1
+
F
2
−
F
1
F
2
⎝
0.010 m
⎛
⎝
⎞
⎠
F
e
=
20.80 D
+
(
−
6.93 D)
−
(
+
20.80 D)(
−
6.93 D)
1.52
F
e
= +
14.82 D
Calculation of f
e
and f
e
′
:
n
′
f
e
′
F
e
=
(1.00)(100)
+
14.82 D
=
f
e
′
f
e
′
= +
6.75 cm
Since the lens is surrounded by air,
f
e
is equal to
6.75 cm. The secondary
equivalent focal length is measured from the secondary principal plane,
and the primary equivalent focal length is measured from the primary
principal plane.
−
Location of principal planes
:
t
⎛
⎞
⎠
F
2
⎝
A
1
H
=
F
e
⎛
⎝
0.010 m
⎞
⎠
(
−
6.93 D)
1.52
A
1
H
=
(100 cm/m)
+
14.82 D
A
1
H
= −
0.31 cm
