# Light question

1. Jul 21, 2010

### dankelly08

Ok so this may be an odd question but maybe there is someone here who can understand what I'm talking about.

When you have a wave of water and the water hits a wall, the waves will ripple back and causes the motion of the waves to traverse.

I was wondering if there is anything like this happens with light? When a torch is pointed at a wall because light acts like a wave does light not traverse backwards in any way at all?

2. Jul 21, 2010

### AJ Bentley

It's called 'a mirror'.

3. Jul 21, 2010

### Staff: Mentor

Whan a water wave strikes a shoreline that is irregular on the scale of about the wavelength or larger, you don't get a coherent reflected wave. Similarly with light. The microscopic irregularities in an ordinary wall prevent a coherent reflected wave. A mirror is very smooth so in that case you do get a coherent reflected wave.

4. Jul 21, 2010

### dankelly08

Thanks :] I have written the question badly..

So really what I'm trying to find out is, if you bounce light off a mirror/wall and when the light beam hits the mirror, is there a change in the light beam at its initial state?

Does the beam (at its initial point) change depending on what type of matter it interacts with?

Does this make sense?

5. Jul 21, 2010

### seto6

yes it gets reflected, if it does not get reflected then you will not be able to see it.

just as AJ Bentley said its a example of a mirror

6. Jul 21, 2010

dankelly08, do you mean to ask: Is the source of the light altered by the reflection of the beam?

(If that is, in fact your question...)I don't know of any reaction between the reflection of emitted photons and the emitter. Perhaps in the case of a reflection from a mirror or other highly reflective surface that is reflected directly back at its source (in your example the element inside the flashlight's bulb), the source might appear more luminous when observed directly.

The reflection of the light, and not its source ("initial point"), is affected by the type of matter it interacts with.

If I've made a mistake here, I'm sure some one will be kind enough to point it out for me

7. Jul 21, 2010

### cragar

The frequency of light being reflected can change .
Raman scattering