Ray Box Investigations For Reflection - Refraction and Total Internal Reflection

1
Ray Box InvestigationsForReflection -
RefractionandTotal Internal Reflection

• Created for CVCA Physics
• By
• Dick Heckathorn
• 1 June 2K 5

2
1
2
30o
30o
60o
60o
3
Rays 1-2-3
3
Conclusion

• The angles are measured from the normal.
• The angle of incidence equals the angle of
  reflection.

4
Reflection
r
N
i
5
Conclusion

• The angles are measured from the normal.
• The angle of incidence equals the angle of
  refraction.
• The incident ray, reflected ray and the normal
  all lie in the same plane.

6
Insert pin into cardboard as shown.
Locate reflection surface of mirror on line.
Reflect ray of light from mirror as shown.
Insert a pin (1) on reflected light ray.
Mark and draw the light rays on paper
Remove mirror
Extend reflected rays behind mirror
The image is located where the rays cross.
Draw a line from object to image
Draw a line across center of paper
Reflect a 2nd ray from mirror as shown
Insert pin (2) on ray and draw it.
Repeat for rays 3 and 4.
How is this line oriented relative to mirror
line?
Repeat for other three occurrences
How does length of red and purple line compare?
Draw normal lines and compare angle i and r
Image
Mirror
i
r
Pin
2
4
1
3
7
Conclusion

• The image is always as far behind the reflecting
  surface (mirror) as the object is in front.
• The line connecting the image and object is
  perpendicular to the reflecting surface (mirror).

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Why know where the image is?
Draw line representing mirror.
Locate object.
Locate image
Locate eye (1)
Connect eye (1) and image
Draw line from object to mirror
Then draw line from mirror to eye 1
Light travels this path from object to pin
Note angle i equals angle r
Repeat for eye 2, 3, and 4
Image
Mirror surface
i
r
Object
Pin
3
1
4
2
9
Conclusion

• Locating the image allows one to predict the path
  light will travel from the object to some
  location.

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I1,2
I1
Mirror (1)
I2
Object
Mirror (2)
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Mirror (1)
Mirror (2)
I1,2
I2
I1
Object
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Periscope
I1
Object
I1,2
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Pepper Ghost
Bottle of Water
90o
Plexiglas
Candle
14
Peppers Ghost
15
Add -60 degree mirrors
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T29-1B
17
T29-1B
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T29-1B
19
19
V
P.A.
F
f
All rays parallel to P.A. reflect back through F
20
Parabolic Mirror
20
21
Circular Mirror
P.A.
Not all rays parallel to P.A. reflect back
through F
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Circular Mirror
P.A.
23

• Go to curved mirror PowerPoint.
• Click

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N
4
i
r
Measure angle i and angle r.
Both 0o
25
5
N
300
i
r
19.50
Calculate
Measure angle i and angle r.
26
N
6
600
i
r
35.30
Calculate
Measure angle i and angle r.
27
Using
for both angles,
what value did you get?
It should be near 1.50
1.50 is called the index of refraction (nP) of
the plastic.
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N
Quiz
750
40.10
Draw an incident ray of 75o.
Calculate the angle of refraction.
Test your drawing with a light ray.
Draw the refracted ray.
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300
600
35.30
19.50
30
N
7
31
N
Bent away/toward normal?
Calculate angle of refraction
Draw the refracted ray
Use light ray to check.
30.90
30.90
200
8
32
n1 sin ?1 n2 sin ?2
It tells us which way the refracted ray bends.
Does it all!!!
What does it do?
How?
The bigger n has the smaller sin ? and thus
the smaller ? (angle).
33
N
Bent away/toward normal?
Calculate angle of refraction
Draw the refracted ray
Use light ray to check.
74.60
74.60
400
9
34
N
Bent away/toward normal?
Calculate angle of refraction
Now what do we do?
Use light ray to check.
Tilt!!
600
600
10
35
N
What happens here?
750
750
11
36
N
37

• Demonstrations
• T.I.R. Plastic
• T.I.R. Water
• T.I.R. Glass Tube
• Ball in/out of Water
• Mugs

38
Demo Aquarium Balls
Aquarium Balls
Air
Water
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300
12
Calculate angle of refraction
Draw the refracted ray.
Which way is ray bent?
n1.50
19.50
Calculate angle of refraction
Which way is ray bent?
Check with ray box.
Draw the refracted ray.
300
40
13
600
600
00
Calculate angle of refraction
Calculate angle of refraction
n1.50
41
11.80
18.20
280
17.80
15
11.80
18.20
280
17.80
14
n1.50
Calculate angle of refraction
Calculate angle of refraction
Calculate angle of refraction
Calculate angle of refraction
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18
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Thats All Folks!! No 16-17