1.

If u is thedistance of the real point object from thte principal focus of a spherical mirror or a focal length f and v is the distance of the real point image from the principal focus, then uv is equal to :

Answer»

f
`f^(2)`
`f^(3)`
`f^(4)`

Solution :(B) Here U = - (u + f) and V = - (v + f)
and F = - f
then `(1)/(u) + (1)/(v) = (1)/(f) rArr - (1)/(u+f)-(1)/(v+f) = - (1)/(f)`
`(1)/(u+f) + (1)/(v+f) = (1)/(f)`
`THEREFORE (u+v+2f)/((u+f)(v+f))=(1)/(f)`
`therefore "" uf + VF + 2f = (u + f)(v + f)`
or `"" uf + vf = 2f^(2) = uf + uf + vf + f^(2)`
Then `f^(2) = uv`
`therefore"" uv = f^(2)`


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