Refraction and Snell's Law

1

Is the eye depicted above nearsighted or
farsighted? 1) nearsighted 2)
farsighted 3) could be either
2
An eyeglass prescription calls for lens powers of
2.1 D for the left eye and 2.5 D for the right
eye. The positive power means the lens is
converging. This person must be A)
nearsighted B) farsighted C) cannot tell
from information given
3
A) nearsighted
Were the object moved even further back, its rays
to the lens would become more parallel, focusing
an image even closer to the lens focal point
(moving the image closer to the focusfurther
from the retina. As the object is moved closer
to the eye, the convergence point of the rays
moves back (toward the retina). So this eye can
focus much better on close objects, but be unable
to focus distant objects.
B) farsighted
A positive lens power means the lens is convex,
or converging. So without the lens, the rays
must converge behind the retina, and so the
person is farsighted.
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8
p 12 cm f1 8 cm
f2 12 cm
40 cm
9
p 12 cm f1 8 cm
p2 40 cm q1 16 cm f2 12 cm
40 cm
Note overall M M1?M2 6
10
p 12 cm f1 8 cm
p2 32 cm 24 cm f2 12 cm
Move the lenses closer together so that the 1st
image is within the 2nds focal point.
32 cm
11
p 12 cm f1 8 cm
p2 32 cm 24 cm f2 12 cm
Move the lenses closer together so that the 1st
image is within the 2nds focal point.
32 cm
Note overall M M1?M2 -6
12
p 12 cm f1 8 cm
p2 16 cm 24 cm f2 12 cm
What if you move the lenses so close
together the 2nd interrupts the formation of
the 1st image?
16 cm
The object is virtual!
13
p 12 cm f1 8 cm
p2 16 cm 24 cm f2 12 cm
What if you move the lenses so close
together the 2nd interrupts the formation of
the 1st image?
16 cm
The object is virtual!
Note overall M M1?M2 1.2
14
A telescope has fo985 mm and fe 50 mm. Find
the angular magnification of the telescope and
its appropriate length.
(a)
(b)
15
The objective of a compound microscope has a
focal length of fo 0.40 cm while that of the
eyepiece is fe 3.0 cm. They are separated by L
20.0 cm. A person with a normal eye (N 25
cm) uses the microscope.

• Find the angular magnification.
• b)What is the greatest angular magnification
• achievable using the eyepiece alone (as a
• magnifying glass)?