Question

An object is placed on 20 cm distance from the optical centre of a convex lens the focal length of a the lens is 30 cm then calculate the object distance and mention the characteristics

Answer 1

using lens formula

-1/u+1/v=1/f

-1/-20+1/v=1/30

1/v=1/30-1/20

1/v = -1/6

v=-6cm

image is enlarged and erect also virtual

Answer 2

ANSWER. 12 cm

given f = 30 cm

u= - 20cm

1/f =1/v +1/ u

1/ 30 = 1/v + 1/ - 20

1/ 30 = 1/ v - 1/20

1/30 + 1/ 20 = 1/ v

1/v =50/ 600

v = 12 cm. Answer