# Light Refection and Snell's Law

1. Jul 21, 2008

### myersb05

The light beam shown in Figure P22.21 makes an angle of ϕ = 23.5° with the normal line NN' in the linseed oil. Determine the angles θ and θ'. (The refractive index for linseed oil is 1.48.)
The normal line makes a 90 angle with the surface of the linseed oil. The light then passes through water but I need the linseed oil angle to get the water angle.

Snell's Law

So I used 1*sin(23.5)=1.48*sin(theta) and solved for theta. I got 15.63 degrees which is incorrect

2. Jul 22, 2008

### Kurdt

Staff Emeritus
If the angle is in the linseed oil then it is the angle after it has been refracted at the air linseed interface. Thats my guess anyway without seeing the diagram.

3. Jul 22, 2008

### Redbelly98

Staff Emeritus
That equation works for an air-to-linseed oil interface or a vacuum-to-oil interface.

You have a water-oil interface; the refractive index of water must enter into Snell's law somehow.

Plus, use Kurdt's suggestion of putting the angle on the correct side of the equation :-)

4. Jul 22, 2008

### Kurdt

Staff Emeritus
I think Redbelly since its asking for two angles that it will be the linseed oil between air and water. Like I said before however, a diagram would be nice.

5. Jul 22, 2008

### Redbelly98

Staff Emeritus
I agree that showing us the diagram would have been helpful, so that we wouldn't have to spend time discussing and guessing at what is going on.