Question

An object is placed in front of a concave mirror of Focal length 20 cm. The image formed is 3 times the size of the object. Calculate 2 possible distances of the object from the mirror.​

Answer 1

Answer:

Also given the image formed is three times the size of the object. is the object distance measured from the left side of the mirror. Therefore, the two possible  of objects from the mirror are 26.67 cm and 13.33 cm from the left side.​

Explanation:

Answer 2

Explanation:

It is given that,

Focal length

f=−20cm

h

i

=3h

o

The image is three times the size of the object. So there are two cases.

Case 1. For real image

m=−

u

v

=−3

v=3u

Using mirror’s formula

f

1

=

v

1

+

u

1

−20

1

=

3u

1

+

u

1

u=

3

−80

cm

Case 2. For virtual image

m=

u

−v

=+3

v=−3u

Again using mirror’s formula

−20

1

=

−3u

1

+

u

1

u=

3

−40

cm

The possible values of u are

3

−80

cmand

3

−40

cm.