11.1 Snell’s Law

Introduction:
Light travels at different speeds in different optical mediums. The different mediums cause light to bend as it changes speed. But the medium is not the only factor affecting refraction. If the incident ray is along the normal, its incident angle is 0° and the ray does not refract. As the angle of incidence increases, the degree of refraction of the ray also increases. In other words, the amount of refraction depends on two factors:
•	The index of refraction
•	The angle of incidence
The relationship is called Snell’s Law and is usually written in the following form:
n1sinΘ1 = n2sinΘ2

Purpose:
To use Snell’s law to find the refractive index of various materials.

Equipment:
-Semicircular plastic piece
-Semicircular water container (cheese box)
-Sugar water, salt water
-Other non-toxic liquids
-Ray box with single slit aperture or laser
-protractor, blank paper

Procedure:
1. On a blank sheet, traced the semicircular shape of the plastic piece.
2. On the straight side of the semicircle, marked the centre and drew a normal at this point.
3. Drew in a series at 10°, 20°, 30°, 40°, 50°, 60°, and 70° from the normal.
4. Darkened the room, and placed the semicircular cheese box containing water on the page, and matched the outline of the semicircle. Shined a ray along the normal to check the position of the box. 
5. Shined the light along the rays drawn on the sheet. Marked the point at which they exit the cheese box, and made sure to keep track of which incident ray goes with each refracted ray.
6. Finished the experiment, removed the cheese box, and drew in the refracted rays. 
7. Measured the angles of refraction.
8. Repeated this experiment using a different liquid or plastic semicircular piece. 








Data & Analysis:
	Angle of INCIDENCE	Angle of REFRACTION	SinΘ1	SinΘ2	SinΘ1
SinΘ2
	0	N/A			
1.	10°	7°	0.17	0.12	1.42
2.	20°	15°	0.34	0.20	1.36
3.	30°	22°	0.5	0.37	1.35
4.	40°	27°	0.64	0.45	1.42
5.	50°	34°	0.76	0.56	1.36
6.	60°	43°	0.87	0.68	1.28
7.	70°	45°	0.94	0.71	1.32

Conclusion:
	With the use of the ray box and the From this experiment, it is evident that the angle of refraction is always going to be less than the angle of incidence when the light travels from rare to dense.