# Help (with prism)

1. Jun 13, 2004

### shingetsunohimitsu

Help

34-31. The prism of the figure has a refractive index of 1.48, and the angles A are 30.0°. Two light rays m and n are parallel as they enter the prism. What is the angle between them after they emerge?
I. Set the hypotenuse of the small triangle to the left at 10cm. Gives you a triangle which is 5^2+8.66^2=10^2
II. The angle should be arccos(5/10)=60.0°
III. The angle of refraction should be arcsin(1.281)
The angle they make with the base of the prism should be arcsin(1.281)+30.0°, In which case the angle they make towards each other is as much 2(arcsin(1.281)+30.0°)

Now, the answer, I'm sure is completely off the hooks.

I'm new around, I don't have a university degree, only what's equivalent to basic high school maths and a burning passion for physics. My dabbling in the arts are meagre, and I want to ask pardon my stupid questions before anyone gets the chance to demand a pardon from me. There you go.
In all my humbleness
/Shingetsu

2. Jun 15, 2004

### Chi Meson

I'm having a hard time picturing the situation. Do the two rays enter the hypotenuse of the triangle with an angle of incidence of 30 degrees? AFter they enter the prism, which internal side do they hit? Do both rays hit the same side internally?

If the two rays are parallel when coming in, and they have do not have different index of refraction, and they hit the same walls of the prism, they should emerge parallel to each other.

And you can't have an arcsin of a number greater than 1.00, so figure out what you meant by that.

3. Jun 15, 2004

### Gokul43201

Staff Emeritus
If you can attach a figure, that will help us understand what's going on. As chi meson said, it's not clear why the emergent rays should not be parallel too - unless they don't go in the same side.

If you have absolutely no means of providing a figure, try describing the prism and the ray directions more clearly.