# A 5cm mirror is just large enough to show the whole image ...

Discussion in 'Physics' started by famous, Nov 24, 2012.

1. ### famous Thread Starter New Member

Nov 24, 2012
3
0
A 5cm mirror is just large enough to show the whole image of a tree when held 20 cm from the eye of the observer whose distance to the tree is 100 m. What is the height of tree?

2. ### MvGulik Member

Nov 3, 2011
40
9
Mmm. Lets see.

Find total light traveling distance.
Divide that by the eye to mirror distance.
Multiply that by height of the mirror.
That should return the height of the tree.

Last edited: Nov 24, 2012
3. ### Markd77 Senior Member

Sep 7, 2009
2,803
594
Try drawing it, essentially I think it is the same as looking through a 5cm hole, you should be able to calculate the ratios of the triangle sides and the height of the tree. (The distance from the eye to the tree should really include the distance to the mirror, and it actually makes a difference which direction you are holding the mirror relative to the tree, but the question is probably ignoring that).

4. ### Syn7 New Member

Nov 13, 2012
11
1
5.1m...........

5. ### atferrari AAC Fanatic!

Jan 6, 2004
2,667
784
Maybe 25 m high? Mental calculation