Question #6dc3b

1 Answer
Dec 15, 2017

i don't know if you are asking for mirror or a lens. So i will answer them both

Explanation:

in case of mirror:
mirror formula is 1f=1v+1u
since f is equal to v,that means
1f=1f+1u.
adding 1f to both sides you get
0=0+1u or,
u=10= , which implies the object was kept at infinity to from image distance equal to focal length.

in case of lens:
lens formula is 1f=1v1u
since f is equal to v,that means
1f=1f1u.
adding 1f to both sides you get
0=01u or,
u=10= , which again implies that the object was kept at infinity to from image distance equal to focal length.

So value of focal length is equal to image distance when object was kept at infinity