# What is the angle of reflection

1. Apr 9, 2004

### math4me

If a beam of light shines from the 10 on the face of a clock, reflects off a mirror in the center and strikes the 5, what is the angle of reflection.

If anyone could help me, it would be much appreciated tyty.

2. Apr 9, 2004

### math4me

any ideas anybody?

3. Apr 9, 2004

### Chen

Connect the 10, the 5 and the reflection points together to form a triangle. What are the properties of that triangle?

4. Apr 9, 2004

### Pergatory

How far is the mirror from the clock? What is the distance from the center of the clock to the 10?

5. Apr 11, 2004

### math4me

Chen i having difficulty could you please explain.

6. Apr 11, 2004

### Staff: Mentor

What's the angle between the hours marked on a clock? For example, what's the angle between 12 and 1? What angle is swept out by the hour hand of a clock each hour?

Then ask what's the angle between the 10 hour mark and the 5 hour mark? (That's 5 hours difference, right?)

A mirror arranged in the center to reflect the light as specified will have angle of incidence plus angle of reflection equal that total angle. So what's the law of reflection have to say?

7. Apr 11, 2004

### HallsofIvy

The mirror is in the center of the clock? Since the "hours" divide the face of the clock into 12 parts, each "hour" division is 360/12= 30 degrees. From 10 to 5 is 5*30= 150 degrees.

8. Apr 11, 2004

### math4me

Ah so the internal angle is 40 degrees, so the angle of reflection is 20 degrees? Am i right anyone??

9. Apr 11, 2004

### Staff: Mentor

Where did you get this? Did you read Halls' answer? (But you are correct that the angle of reflection will equal half of the total angle.)

10. Apr 11, 2004

### math4me

Yes Hall helped me ty v much everyone it is much appreciated. :-)