# Critical Angle Problem

• qszwdxefc
In summary, the critical angle for a special glass in air is 44 degrees, but when the glass is immersed in water, the critical angle increases to 68 degrees due to the difference in refractive indices. This can be calculated using the equation sin(critical angle) = 1/index of refraction, where the index of refraction of air is 1.00 and the index of refraction of water is 1.333. Snell's Law can also be used to determine the critical angle.

## Homework Statement

The critical angle for a special glass in air is 44 degrees. What is the critical angle if the glass is immersed in water?

## Homework Equations

sin(critical angle) = 1/index of refraction

index of refraction of air is 1.00
index of refraction of water is 1.333

## The Attempt at a Solution

I have no clue where to start that's the problem :S.

Just for reference, the textbook answer is 68 degrees.

Thanks.

qszwdxefc said:
sin(critical angle) = 1/index of refraction
Hint: That's only true if the surrounding medium has n = 1. (How is the critical angle formula derived?)

Ah, Snell's Law where $$\theta_2$$ = $$90^\circ$$.

Thanks.

Last edited:
Have you tried using the eqaution n1sinQ=n2sinQ
by the way the one is just saying its the first refractive index, and the Q is theta.
Maybe you could try this eqaution.
Thanks I hope that helps...

qszwdxefc said:

## Homework Statement

The critical angle for a special glass in air is 44 degrees. What is the critical angle if the glass is immersed in water?

## Homework Equations

sin(critical angle) = 1/index of refraction

index of refraction of air is 1.00
index of refraction of water is 1.333

## The Attempt at a Solution

I have no clue where to start that's the problem :S.

Just for reference, the textbook answer is 68 degrees.

Thanks.