An object of height 1.5 cm is placed on the axis of a convex lens of focal length 25 cm. A real image is formed at a distance of 75 cm from the lens. The size of the image will be

Question

An object of height 1.5 cm is placed on the axis of a convex lens of focal length 25 cm. A real image is formed at a distance of 75 cm from the lens. The size of the image will be (A) 4.5 cm (B) 3.0 cm (C) 0.75 cm (D) 0.5 cm

Tardigrade Admin · Accepted Answer

Magnification m=(I/O)=(-v/u) Given: O=1.5 cm By, lens formula (1/f)=(1/v)-(1/u) (1/25)=(1/75)-(1/u) or u=-(75/2) cm ∴ (I/1.5)=-(75/(-75 / 2)) or I=3 cm

Q. An object of height $1.5 c m$ is placed on the axis of a convex lens of focal length $25 c m$ . A real image is formed at a distance of $75 c m$ from the lens. The size of the image will be

4.5 cm

3.0 cm

0.75 cm

0.5 cm

Magnification $m = \frac{I}{O} = \frac{- v}{u}$
Given: $O = 1.5 c m$
By, lens formula
$\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$
$\frac{1}{25} = \frac{1}{75} - \frac{1}{u}$
or $u = - \frac{75}{2} c m$
$∴ \frac{I}{1.5} = - \frac{75}{( - 75/2 )}$
or $I = 3 c m$

Q. An object of height 1.5cm is placed on the axis of a convex lens of focal length 25cm. A real image is formed at a distance of 75cm from the lens. The size of the image will be