# what is a focal length of plane mirror

@your friends have answered this question very well. keep it up students.

In case of convex and concave mirrors (i e spherical mirrors) , the centre of curvature is the centre of the sphere of which the mirror forms a part and the radius of curvature is the radius of the sphere of which the mirror forms a part. The focal length is half of the radius of curvature. Now , let us imagine plane mirror to be a part of a sphere with infinite radius. As a result, the focal length will be infinity.

• 5

Full define;-

• -11

Infinity.because the distance of object from mirror"p" and the distance from image to mirror"q" are equal,so by using formula
1/f=1/p+1/q
as the image of plane mirror is virtual,so"q" is taken negative,so putting values
1/f=1/p-1/p(bcz p=q)
1/f=0
f=1/0
and any thing divided by zero is infinity.

• 17

Focal length of plane mirror is the distance between the centre of curvature and the focus.

f = dis. b/w C and F.

• -13

Focal length of a plane mirror is infinite because we know that focal length of mirror is R/2. But the radius of curvature of plane mirror is infinte so infinit/2 is also a infinite value.

Note:- Plane mirror can be considered as concave mirror of infinte radius.

• 47
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