# Optics - How long can I see an objects reflection

1. Nov 5, 2009

### Paulo Serrano

Optics -- How long can I see an objects reflection

1. The problem statement, all variables and given/known data
The object is traveling at a constant velocity of 4 m/s. Initially, the observer can not see the object. At a certain point, the observer can see the reflection of the object in the mirror. For how many seconds is the observer able to see the reflection of the object on the mirror?

http://img32.imageshack.us/img32/8514/mirrorquestion.jpg [Broken]

2. Relevant equations

Don't know.

3. The attempt at a solution

I know that you have to see if the observer's image on the other side of the mirror can see the object to determine if it's visible to the observer. That's all I know, really. Does it have something to do with similar triangles?

Last edited by a moderator: May 4, 2017
2. Nov 5, 2009

### mgb_phys

Re: Optics -- How long can I see an objects reflection

Light reflects from a mirror at the same angle (to the normal) that it arrives.