PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 62)

Introductory Optics System 012-02744K
®
56
Exp 6: Dispersion and Total Internal Reflection
Dispersion
➀
Color separation was first noted at about 40°, al-
though it may be noticeable before then depending
on the light in the room.
➁
Maximum separation occurs at about 85°; beyond
that the violet is totally internally reflected.
➂
In order: (although not all colors may be resolvable
depending on the room light) red, orange, yellow,
green, cyan, blue, violet.
➃
With an incident angle of 40°, the violet was at 76°
and the red was at 73°.
n
red
= 1.488
n
violet
= 1.510
Total Internal Reflection
➀
The reflection occurs mainly at the internal flat side
of the lens.
➁
There is a reflected ray for all angles.
➂
The reflected ray is consistent with the law of re-
flection.
➃
There is not a refracted ray for all angles of inci-
dence. Beyond 43°, the light is totally internally
reflected.
➄
The intensity of the reflected ray increases with the
angle of incidence; the intensity of the refracted
ray decreases.
➅
All the light is reflected when the angle of refrac-
tion reaches 90°. This occurs for an angle of inci-
dence of about 43°.
Exp 7: Converging Lens: Image and Object Relationships
Suggestions on – Procedure
➀
The image magnification will depend on the rela-
tive placement of the lens. For any target-to-screen
distance of more than four times the focal length,
there will be two lens positions which will focus
the image. One of these positions will enlarge the
image, one will reduce it.
➁
The image will be inverted regardless of magnifi-
cation.
➂
Increasing d
o
will decrease d
i
.
➃
As d
o
goes to infinity, d
i
goes to the focal length of
the lens.
➄
Use the lens to focus an image of a very distant ob-
ject on the screen (d
o
should be greater than two
meters - preferably much longer.) Measure the im-
age distance; it will be approximately equal to the
focal length of the lens.
do (mm) di hi 1/di + 1/do 1/f hi/ho -di/do % f % m
500 87 -3.5 0.01 0.01 -0.18 -0.17 1.19% 5.54%
450 90 -4.0 0.01 0.01 -0.21 -0.20 0.00% 5.00%
400 93 -4.5 0.01 0.01 -0.24 -0.23 -0.61% 1.83%
350 96 -5.5 0.01 0.01 -0.29 -0.27 -0.45% 5.25%
300 100 -6.5 0.01 0.01 -0.34 -0.33 0.00% 2.56%
250 107 -8.0 0.01 0.01 -0.42 -0.43 0.09% -1.65%
200 120 -11.5 0.01 0.01 -0.61 -0.60 -0.00% 0.87%
150 149 -19.0 0.01 0.01 -1.00 -0.99 0.33% 0.67%
100 300 -58.0 0.01 0.01 -3.05 -3.00 0.00% 1.72%
75
50