Question

the image of an object placed at 60 cm infront of a lens is obtained on a screen at a distance of 120 cm from it .Find the focal length of the lens .What would be the height of the image when the object is 3 cm high​

Answer 1

Answer:

10cm

Explanation:

Object distance u = -60 cm

Image distance v = +120 cm

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

1/f = 1/120 - ( -1/60 ) = 1/120 + 1/60 = 3/120 = 40

f = +40 cm

H(image) / H(object) = v/u

Hi = -120/60 X 5 = -10 cm :)