PHY13L - E404 - Index of Refraction

1.       If the transparent material has an index of refraction of 1.60, what is the angle of incident beyond which total internal reflection occurs?

Using the Snell's Law equation wherein the angle of incident when the angle of refraction becomes 90^o is called the critical angle if incident. Solving for it when the index of refraction is 1.60:

The angle of incident beyond which total internal reflection occurs is .

2.       Is it possible for the critical angle to exist when light goes from air (n=1.00) into water (n=1.33)? Explain your answer.

Critical angle will not be existing when light goes from air into water. Theoretically, n₂ which is index of refraction of the second medium wherein this case is the water must be less than n₁ which is the index of refraction of air as stated in Snell's Law. Therefore, it is not possible.

PROBLEMS

 

1.       A ray of light from air, incident at an angle of 60^o on top of a transparent surface, is refracted and reflected partly. It is observed that the refracted and reflected rays are perpendicular to each other. Find the index of reflection and velocity of light in the transparent surface.

 

 

DATA and OBSERVATIONS

PARTS A and B. Determination of Index of Refraction of Glass

	PART A Light bends from GLASS to AIR	PART B Light bends from AIR to GLASS
Length of line GH	3.35cm	4.90cm
Length of line FL	5.00cm	3.25cm
Index of Refraction of Air, na	1.0	1.0
Index of Refraction of Glass, ng (experimental value)	1.49	1.51
Index of Refraction of Glass, ng (accepted value)	1.5	1.5
Percentage error	0.66%	0.66%

 

PART C. Determination of Critical Angle

 

Length of line MU	5.20cm
Length of line EU	6.40cm
Critical Angle, θC (experimental value)	39.09°
Critical Angle, θC (accepted value)	41.81°
Percent Error	6.51%

 

 

 

SAMPLE COMPUTATION

PART A

PART B

PART C

 

 

ANALYSIS

1.       Why can't a material have an index of refraction less than 1.00?

Since nothing can travel faster than the speed of light according to the theory of relativity, the speed of light in vacuum is always faster the speed of light in a medium so the index of refraction cannot have a less than 1.00.

2.       Does the angle of incidence affect the index of refraction of a materiel? Explain your answer.

The index of refraction is not affected by the angle of incidence of a material since the index of refraction has a constant value depending on a material or medium.

3.       What happens to the wavelength of light when it is refracted? Consider a case where light enters a denser medium.

The velocity of light wave decreases then light enters a denser medium while the frequency is stayed constant, the wavelength of refracted light increases.

CONCLUSION

Therefore I conclude that the index of refraction of a medium do not change even after seeing  it in 2 ways, one from less dense to more dense and second from more dense to less dense. I also found out that the angle of refraction is near the normal line if the condition was from less dense to more dense.

Also, we can only get critical angle when the first medium has higher index of refraction than the second medium. If the index of refraction of the first medium is less than the second medium, we cannot get the critical angle because the less dense will reach its critical angle first than the second medium in which obeys the Snell's Law.