Question

An object 5 cm high is located 20 cm from a
concave mirror, whose focal length is 25 cm. Make
an accurate scale diagram and hence locate the
position of the image and find its size. Also, state
the nature of the image.​

Answer 1

Explanation:

Given data :- Ho(height of object) = 5cm

u(object distance) = - 20cm

f(focal length) = - 25

As we know that in concave mirror and in concave lens, focal length is always NEGATIVE .

Now, by Mirror Formula,

1/f = 1/v + 1/u

1/f - 1/u = 1/v

1/-25 - 1/-20 = 1/v

1/-25 + 1/20 = 1/v

20 - 25/-25 x 20 = 1/v

-5/-500 = 1/v

1/100 = 1/v

v = 100 cm

:- As the image distance is in POSITIVE sign, the nature will be VIRTUAL & ERECT.

Now Magnification,

M = Hi/Ho = -v/u

M = Hi/5 = - 100/ -20 (Minus sign will be cancelled)

M = Hi = 100 x 5 / 20

M = Hi = 25 cm

:- Hence, the size of image will be enlarged.

(Please draw diagram at your own)

Please mark it as the Brainliest answer.

Thank you!

Answer 2

Explanation:

Formula:

v

1

+

u

1

=

f

1

Given,

v

1

+

(−20)

1

=

15

1

v

1

=

60

7

⇒v=

7

60

v=8.57≈8.6cm

The image is formed behind the mirror at a distance of 8.6 cm

m=

h

1

h

2

=−

u

v

→

5

h

2

=−

20

8.57

∴h

2

=2.175 cm

Thus the image is 2.175 cm high, virtual and erect.

Hence, this is the answer.