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# Refraction watch

1. Having trouble with the second part of this question

A light ray enters an equilateral glass prism of refractive index 1.55 at the midpoint of one side of the prism at an angle of 35 degrees.
Show that the angle of refraction is 22 degrees.

Show that the angle of incidence where the light ray leaves the glass prism is 38 degrees.

Also, a bit unrelated but why does the shape of glass have to be a prism in order to create a spectrum of colours due to refraction? Why wouldn't it work with a glass cube, for example?
2. I think for the second part you'll need to draw a sketch of the prism & rays so you can work out by geometry at what angle the ray inside the class meets the other surface - then just use Snell's law as before to find the angle at which it emerges.

For the cube thing, since the sides of a cube are parallel, the ray refracts in one direction on enetering but in the opposite direction on leaving. So, although the colours will be dispersed inside (maybe not enough to see) they will come back together as the ray leaves the cube.

Using a prism, the light is refracted as it enters the prism then refracted further as it leaves the prism so rather than the dispersion being cancelled or undone by this second refraction, it is increased.
3. (Original post by phys981)
I think for the second part you'll need to draw a sketch of the prism & rays so you can work out by geometry at what angle the ray inside the class meets the other surface - then just use Snell's law as before to find the angle at which it emerges.

For the cube thing, since the sides of a cube are parallel, the ray refracts in one direction on enetering but in the opposite direction on leaving. So, although the colours will be dispersed inside (maybe not enough to see) they will come back together as the ray leaves the cube.

Using a prism, the light is refracted as it enters the prism then refracted further as it leaves the prism so rather than the dispersion being cancelled or undone by this second refraction, it is increased.
I couldn't get the answer to the first but thank you for the explanation of the prism!
4. (Original post by G.Y)
I couldn't get the answer to the first but thank you for the explanation of the prism!
See if this helps with the angles, it's impossible to describe in words.

For some reason I can't attach it so try here https://drive.google.com/file/d/1vLj...ew?usp=sharing
5. (Original post by phys981)
See if this helps with the angles, it's impossible to describe in words.

For some reason I can't attach it so try here https://drive.google.com/file/d/1vLj...ew?usp=sharing
Oh, thank youuu

It appears I can't give you rep as I've already done so recently but much appreciated

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