1.) A light beam goes from a medium with index of refraction 1.6 into another me

Question

1.) A light beam goes from a medium with index of refraction 1.6 into another medium with index of refraction 3.5.
Inside the new medium, which of the following is true?
The frequency becomes higher.
The wavelength becomes longer.
The wavelength stays the same.
The light beam moves with the same velocity.
The wavelength becomes shorter.

2.) What is the critical angle of total internal reflection?
16.6°
27.2°
38.7°
None of the above.

3.) What is the critical angle of total internal reflection if the beam direction is reversed, i.e., if the beam goes from the medium with index of refraction 3.5 into the medium with index of refraction 1.6?
16.6°
27.2°
38.7°
None of the above.

Explanation / Answer

1.

index of refraction is,

n = c/v

here, c is speed of light in vacuum and v is speed of light in medium.

index of refraction is inversely proportional to v.

for first medium, index of refraction is 1.6 [lower]

for second medium, index of refraction is 3.5 [higher]

So speed of light decreases when it goes to second medium.

the speed of light is,

v = frequencyxwavelength

speed of light is directly proportional to wavelength.

So, the wavelength also decreases, but the frequency of light does not change.

hence,

The frequency becomes higher [false]
The wavelength becomes longer [false]
The wavelength stays the same. [false]
The light beam moves with the same velocity [false]
The wavelength becomes shorter [true]

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