# Refractive index question

1. Oct 11, 2004

### benhorris

Light ray goes into a container at 70 degrees, the container is made of perspects. The refective index of perspex is 1.48.

What are the angles of refraction in (i) the water; (ii) the plastic, (iii) the air below the tank.

I cant work it out, the answer to the first bit is 26 degrees, i know that for sure, thanks....

2. Oct 11, 2004

### Sirus

Please show us what you have done so far and where you are stuck.

3. Oct 11, 2004

### benhorris

ok using snells law, n (refractive index) = sin i / sin r, i have worked out the first one which equals

sin 20 / 1.33 = sin r (the refractive index is 1.33 for water)

= 26 degrees

next i need to find the refractive index of the perspects which is 1.48, done!
the hint for the question is " You need to work out the refractive index when light goes from water to plastic – just imagine a thin layer of air between them."

hum, i thought, i tryed all different ways of doing it with out any joy, so im stuck, confused and irritated.

4. Oct 11, 2004

### benhorris

Please note that the container is made of perspects, filled with water. The orginal ray of light came into the water at 70 degrees and i have worked out that the refraction of the light ray is 26 degrees. Just need to find the other two parts to the question...