Question

an object of height 4 cm displaced at the distance of 20 cm from a concave mirror of focal length is 15 cm find the nature position and height of image

Answer 1

Answer:

h1 = 10cm, u = -36cm, f = -12cm

We know that

1/v + 1/u = 1/f

⇒ 1/v + 1/(-36) = 1/(-12)

⇒ 1/v = 1/36 – 1/12 = (1 – 3)/36 = - (2/36) = - (1/18)

∴ The position of the image is 18 cm in front of the mirror.

Magnification, m = h2/h1 = - (v/u)

⇒ h2/10 = - ((-18)/(-36))

⇒ h2 = -5 cm

The image formed is real and inverted

Answer 2

height of object = 4 cm

object distance = -20 cm

focal length = -15 cm

image distance = 1/v + 1/u = 1/

1/v + 1/-20 = 1/-15

1/v - 1/20 = 1/-15

1/v = 1/20 - 1/15

1/v = 3-4/60

1/v = -1/60

v = -60

height of image = h'/h = -v/u

h'/4 = -(-60)/-20

we will cut minus and zeroes

h' = -3×4

h' = -12

hence, position of image= -60

height of image = -12

nature of image = real and inverted

Step-by-step explanation:

• The image and height of image for real image is negative. So it is a concave mirror.