Question

A concave mirror of focal length 1.5m forms an image of an object placed at a distance of 40cm. Find the position and nature of the image.

Answer 1

Solution: F= -1.5 m=-150cm

object distance i.e u=-40cm

according to mirror formula,

1/F = 1/V + 1/U

-1/150 = 1/V -1/40

1/V= -1/50+1/40

1/V= -4/200+5/200

1/V=1/200

V=200cm

position between c and F

nature: Real and inverted

Answer 2

Image formed at 54.54 cm behind the mirror. It is virtual and erect.

Explanation:

Given: Focal length of the mirror f = -1.5m = -150 cm

Object distance u = -40 cm  

Solution:

According to mirror formula, we know that 1/f = 1/v + 1/u

1/-150 = 1/v + 1/-40

1/v = 1/40 - 1/150

1/v = 1/40 - 1/150

1/v = 15/600 - 4/600

1/v = 11/600

1/v = 600/11

Therefore v = 600/11 = 54.54 cm

Since the image distance is a positive value, we infer that the image is formed behind the mirror at a distance of 54.54 cm. It is virtual and erect.