Question

a 5cm tall object placed perpendicular to the principal axis of a convex lens of focal length 10cm. the distance of the object from the lens is 30cm. find the size from the lens

a) 1cm
b) 1.5cm
c) 3cm
d) 2.5cm

Answer 1

Answer:

c

Step-by-step explanation:

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Answer 2

Answer:

The subject should be physics not Mathematics. however,

given:

height of obj. = 5cm

focal length of convex lens = 10cm

object distance (u) = -30cm (obj distance should be taken -ve)

objective: find image height.

lens formula= 1/v - 1/u = 1/f

1/v - 1/-30 = 1/10

1/v = 1/10 + 1/-30

(find LCM)

1/v = 3/30 + (-1/30)

1/v = 2/30

(flip both sides)

v/1 = 30/2

v = 15.5 cm

now we have image distance we can start finding its height.

hi/ho = v/u

x/5 = 15.5/-30

x = 15.5/-30 * 5

x = 15.5/-6

x = -2.5

therefore hi = -2.5

option D is correct!