Question

an object of height 4 cm is placed in front of a concave lens of focal length 40 cm if the object distance is 60 cm find the position and height of the image
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Answer 1

ANSWER:

Here,

V=?

U = -60

F = -40

Lens formula is:-

1/V -1/U =1/F

1/V -1/(-60) = -1/40

1/V + 1/60 = -1/40

1/V = -1/40-1/60

1/V = (-30-20)/120

1/V = -50/120

1/V = -5/12

V = -12/5

V = -2.4cm

magnification :-

m = h²/h¹ and

m = v/u

therefore, h²/h¹ = v/u

h²/4 = -2.4/60

h²×60 = -2.4 × 4(by cross multiplication)

h² = -9.6/60

h² = 0.16