Biomedical Engineering Reference
In-Depth Information
A
n
′
= 1.52
Real image
L
′
= +3.80 D
40.00 cm
B
n
= 1.00
n
′
= 1.52
Virtual image
L
′
= -3.80 D
40.00 cm
Figure 3-2.
A.
When the converging light rays that form an image exist in glass, the
refractive index of glass is used to calculate the image vergence.
B.
Since the diverg-
ing light rays that form the virtual image exist in glass, the refractive index of glass is
used to determine the image vergence.
What is the vergence of the rays forming the virtual image in Figure 3-2B?
The key is to recognize that the rays forming the image exist in the secondary
medium, glass. They
appear
to emerge from a point in the primary medium (air),
but “live” in glass. Therefore, the image vergence is calculated as
n
′
′
=
L
′
l
1.52
0.40 m
L
′
=
