Solving Plane Mirror Question: How Far is the Flagpole?

[dev-hud]

If you hold a 900cm squared plane mirror 45 cm from your eyes and can just see the full length of an 8.5 m flagpole behind you, how far are you from the pole.



I am doing mirror/lens questions and for some reason this one stumps me. I am assuming that the 8.5 m has to be changed to cm. However, i have been dealing with questions of radius of curvature and focal length and then this one seems really easy but it has stumped me? can anybody help please?

 

[berkeman]

If you hold a 900cm squared plane mirror 45 cm from your eyes and can just see the full length of an 8.5 m flagpole behind you, how far are you from the pole.



I am doing mirror/lens questions and for some reason this one stumps me. I am assuming that the 8.5 m has to be changed to cm. However, i have been dealing with questions of radius of curvature and focal length and then this one seems really easy but it has stumped me? can anybody help please?

Convert the area you are given for the mirror into its height. Then use a sketch to figure out the triangles to get to the answer. And yes, you need to be consistent with your units. I'd put everything in mks, myself.