Posted by Juniper on .
"Show mathematically that to produce an image that is the same size as the object in a concave mirror, the object needs to be at twice the focal length from the mirror."
and bobpursley answered:
"1/o + 1/o=1/f
1/2f + 1/i=1/f
M=di/do= 2f/2f= 1
check my thinking."
could someone please explain, I'm not really following.
Physics - urgent, please help! -
the mirror equation
1/do+ 1/di= 1/f I assume you are familiar with that. I see I had a typo in the first line.
multiply by do
but M (do/di=ho/hi= 1 given)
1+1=do/f which means that do is twice f.