Question

A concave mirror of focal length 10cm forms an image of a object which is twice in size of the object find the object distance for the real image

Answer 1

Answer:

I don't know this answer for yourself

Answer 2

Answer:

The answer is the object should be placed at a distance of 5 cm

Explanation:

Given:

Focal length, (f) of the concave mirror = −10 cm

To find: Distance of the object, u from the mirror.

Solution:

Case-1

The image is real, and its magnification, m is −2.

From the magnification formula, we know that-

m=−vu

Substituting the given values in the magnification formula we get-

−2=−vu

−2u=−v

v=2u

Now, from the mirror formula, we know that-

1f=1v+1u

Substituting the given values in the mirror formula we get-

1(−10)=12u+1u

1−10=1+22u

1−10=32u

2u=−10×3

u=−10×32

u=−15cm

Thus, the object should be placed at a distance of 15 cm in front of the concave mirror.

Case-2

The image is virtual and its magnification, m is +2.

From the magnification formula, we know that-

m=−vu

Substituting the given values in the magnification formula we get-

−2=−vu

−2u=−v

v=2u

Now, from the mirror formula, we know that-

1f=1v+1u

Substituting the given values in the mirror formula we get-

1(−10)=1(−2u)+1u

1−10=−12u+1u

1−10=−1+22u

1−10=12u

2u=−10

u=−102

u=−5cm

Thus, the object should be placed at a distance of 5 cm in front of the concave mirror.

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