Refraction Of Light

Purpose: To investigate the behavior of light when it passes from air into an optically denser medium.

Prediction / Hypothesis: When the light (incident ray) passes from air into an optically denser medium with an angle of incidence equal to zero, there would be no refraction. When the light passes at an angle from air into an optically denser medium, the light (incident ray) will immediately change direction and bent towards the normal which has an angle of incidence of 0&#61616;.

Method:
1. The semicircular plastic block was placed on the center of the backside of a clean page in the lab book. Then, its outline was traced and the location of the center of the center of the flat side was marked.

2. A single ray of light from the ray box was directed to the center of the flat side at an angle of incidence of about 0&#61616;. The location and direction of both the incident and emergent rays were marked.

3. Without moving the block, the raybox was moved and was still directed at the center of the flat side but the angle of incidence is about 15&#61616;. Then it is labeled (2) for ¡°second set of rays¡±.

4. This was repeated until about fifteen incident and emergent ray pairs with angles of incidence ranging from about 0&#61616; to 89&#61616; were obtained.

Diagram:

Apparatus:
1) Ray box
2) Semicircular plastic block

Observations/Analysis:

# of the ray set Angle of incidence (I) Angle of refraction (R) Sin<I Sin<R
1 0&#61616; 0&#61616; 0 0
2 15&#61616; 10&#61616; .25 .17
3 22&#61616; 12&#61616; .37 .2
4 26&#61616; 19&#61616; .43 .32
5 30&#61616; 22&#61616; .5 .37
6 37&#61616; 23&#61616; .6 .39
7 40&#61616; 26&#61616; .64 .44
8 48&#61616; 29&#61616; .74 .48
9 53&#61616; 30&#61616; .79 .5
10 58&#61616; 34&#61616; .84 .55
11 62&#61616; 38&#61616; .88 .61
12 68&#61616; 41&#61616; .92 .65
13 74&#61616; 44&#61616; .96 .69
14 81&#61616; 46&#61616; .98 .71
15 82&#61616; 48&#61616; .99 .74

- As a ray of light passes from air into glass, the ray of light is bent towards the normal.
- This is always the case when light passes from one medium to another that is optically denser.

Conclusions:
From the experiment, we can see that as the angle of incidence increases, the angle of refraction decreases. The sin <I vs. sin<r graph shows that

Sin <I = constant
Sin <R

The ratio of the sine of the angle of incidence to the sine of the angle or refraction is a constant (also known as Snell¡¯s Law)

Sources of error:
The measurements were not accurate.
Some rays might not pass through the center of the block.

Category: Science