Question

a canvex lens forms a real and inverted image of a needle at a distance of 50 from it where is the needle placed in front of the canvex lens if the image is equal to the size of the object? also find the power of the lens​

Answer 1

Answer:

Object distance (u)= – 50 cm

Image distance (v)= 50 cm

Focal length = f ,

According to the lens formula,

u = -50 cm ; v = + 50 cm ; f =?

1/f = 1/v + 1/u

1/f = 1/50 + 1/50

f = + 25 cm  = 0.25 m

Power of lens (P) = 1/f

                            = 1/ 0.25 = + 4D.