Refractive index &

critical angle of a material Set-UP Procedure 1) To verify the Snell's Law

2) determine the refractive index &

critical angle of a semi-circular glass

block with respect to air We should have

1) Ray Box

2) Paper Protractor

3) Semicircular Glass Block 1) Put the semi-circular glass block on the paper

protractor and it should be aim at 90 degree edge

2) Open the ray box's light bulb

3) Turn off classroom's light

4. Measure the angle of incidence i and the

angle is refraction r and write the value on the

table

5. Repeat step 4 with different values of i. Observe

and changes in the reflected ray and refracted ray

6. Plot a graph of sin i and sin r Objective Glass is denser than air. As the ray

leaves the glass block it refracts away

from the normal.If the angle of incidence

is greater than the critical angle, total internal reflection occurs. If n is the refractive index of a medium,

and C is the critical angle then -Draw a graph of Sin i (y-axis) against Sin r (start both axes at zero).

-A straight line graph (best fit) through the origin shows that Sin i is proportional to Sin r.

- Select two suitable points on the graph (far apart) to find the slope of the graph. This is an average value for the refractive index of the medium. Graph

- Carefully draw a normal line at the point of

incidence to help you to place the protractor

properly

- Avoid using small angles of incidence as

errors in reading the angles would then be

relatively large

- Place two dots far apart on the incident and

refracted light beams to accurately locate

the beams

Precautions: Group member:

5E Lee Kim Lun (11)

5E Tsang Lai Chu (32)

5D Cheung Ying (26)

5D Chan Nga Ching (23) Physics SBA Background Snell's Law

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