# Homework Help: Angle between the incident ray and the reflected ray?

1. Feb 22, 2005

### jai6638

A ray of light strikes a mirror at an angle of 53 degrees to the normal.

A) what is the angle of reflection?
Ans: 53 degrees

B) what is the angle between the incident ray and the reflected ray?
Ans: 53+53 = 106 degrees

C) A ray of light has an angle of incidence of 30 degres on a block of quartz and an angle of refraction of 20 degrees. What is the index of refraction for this block of quartz?
Ans: Nr = (1.54) (sin 30) / (sin20) = 2.25

thanks

Last edited: Feb 22, 2005
2. Feb 22, 2005

### Davorak

Where did the 1.54 com from in:?
"Nr = (1.54) (sin 30) / (sin20) = 2.25"
Is the light ray in air before it hits the quartz? I am assuming so. So one of your indexes of refraction in the above equation should be 1 since 1 is the index of refraction of air.

3. Feb 22, 2005

### jai6638

but.... dont i have to specify the index of refraction of quartz which is 1.54..... i dont see where the index of refraction of air would fit in..

EDIT: nevermind figured it out... so basically it'll be Nr= sin 30/sin20?

Last edited: Feb 22, 2005
4. Feb 22, 2005

### Davorak

Yes that looks good with the edit

5. Feb 22, 2005

### jai6638

great.. thanks much :)

6. Feb 23, 2005

### Davorak

No problem and thank you for the response at the end it is nice to know that I helped.

7. Feb 23, 2005

### HallsofIvy

The problem ASKED for the index of refraction of quartz! Actually there are different kinds of quartz that have slightly varying indices of refraction. Since sin(30)/sin(20)= 1.46, that's not too far off your value.

8. Feb 23, 2005

### Davorak

Yeah I looked it up. It think this type of quartz is Fused quartz, do either of you know the difference between fused quartz and just plain old quartz?