Question

A converging lens of focal length 6.25 cm is used as a magnifying glass. If the near point of observer is 25 cm from the eye and lens is held closeto the eye, calculate the distance of the object from the lens , angular magnification

Answer 1

Hello friend,

Given -

f = 6.25 cm

Image is formed at near point of observer, thus

v = -25 cm

D = 25 cm

u = ?

m = ?

Solution -

a)Putting these values into equation,

1/f = 1/v-1/u

1/6.25 =-1/25 - 1/u

1/u =- 1/6.25 -1/25

1/u = (-4-1)/25

u = - 5 cm

Hence object is at distance of 5cm.

b) Angular magnification when object is placed at close to focus point is given by -

m = 1 + D/f

m = 1+ 25/6.25

m = 1+4 = 5

Hence angular magnification is 5.

Hope it was useful.

Answer 2

I am not sure about the answer please explain it correctly