Concave Mirror

An object of height 4 cm is placed upright in front of spherical concave mirror at a distance of 20 cm and forming an inverted image of 16 cm high. Find the radius of mirror

Thanks Omi,

I was wondering about this one.  I want to take a really good look at your answer ...

Hopefully i will do that tomorrow :)

Omi67,

Why is the focal length a half of the radius ?

I understand very little of this type of physical problem but if you could give me a reason that would be great.  ://

Thanks :)