The focal length of a simple convex lens used as a magnifier is 10 cm . For the image to be formed at a distance of distinct vision D=25 cm , the object must be placed away from the lens nearly at a distance of

Question

The focal length of a simple convex lens used as a magnifier is 10 cm . For the image to be formed at a distance of distinct vision D=25 cm , the object must be placed away from the lens nearly at a distance of (A) 5 cm (B) 7 cm (C) 8 cm (D) 16 cm

Tardigrade Admin · Accepted Answer

f=+10 textcm. v=25 textcm. (1/v)-(1/u)=(1/f) (1/25)-(1/u)=(1/10) (10 - 25/250)=(1/u) u=16 text cm

Q. The focal length of a simple convex lens used as a magnifier is $10 c m$ . For the image to be formed at a distance of distinct vision $D = 25 c m$ , the object must be placed away from the lens nearly at a distance of

$5 c m$

$7 c m$

$8 c m$

$16 c m$

$f = + 10 cm.$
$v = 25 cm.$
$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
$\frac{1}{25} - \frac{1}{u} = \frac{1}{10}$
$\frac{10 - 25}{250} = \frac{1}{u}$
$u = 16 cm$

Q. The focal length of a simple convex lens used as a magnifier is 10cm . For the image to be formed at a distance of distinct vision D=25cm , the object must be placed away from the lens nearly at a distance of

5cm

7cm

8cm

16cm