Question

a concave mirror of focal length 20 cm produces an image twice the height of the object. if the image is real then the distance of the object from the mirror is​

Answer 1

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Answer 2

Correct Question -

A concave mirror of focal length 20 cm produces an image twice the height of the object.

If the image is real then the distance of the object from the mirror is ........

Solution -

In the above question, we have the following information -

A concave mirror of focal length 20 cm produces an image twice the height of the object.

The image is real .

let the distance of the object from the mirror be u.

let the distance of the image from the mirror be v.

Here, the image is twice the height of the object .

Hence the magnification of the mirror is 2.

So,

Magnification = [ - v ] / [ u ]

SO,

V = -2 U.

According to the mirror formulae ,

( 1 / u ) + ( 1 / v ) = ( 1 / f )

Substituting the given values ,

( 1 / u ) - ( 1 / 2u ) = ( - 1 / 20 )

( 1 / u ) { 1 / 2 } = (- 1 / 20 )

u = - 10

Hence, the image is real .