Question

A point object is placed at a distance of 12 cm from a convex lens on its principal axis. Its image is
formed on the other side of the lens at a distance of 18 cm from the lens. Find the focal length of the
lens.​ draw a ray diagram​

Answer 1

Answer:

u = -12 cm

v = 18 cm

f = ?

1/v - 1/u = 1/f

1/f = 1/18 - 1/-12

= 1/18 + 1/12

= 2 + 3/36

= 5/36

f = 36/5

f = 7. 1 cm

Answer 2

Answer:

Hey Mate...

..here is ur answer...

..

》The focal length of the lense is...

..

distance of image = 18cm

distance of object = 12cm

...FORMULAE..

..

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ \frac{1}{18} - \frac{1}{</em><em>-</em><em>12} = \frac{1}{f} \\ \frac{12 </em><em>+</em><em> 18}{216} \\ .. \\ \frac{</em><em>30</em><em>}{216} = \frac{1}{f} \\ .. \\ \frac{ </em><em>72</em><em>}</em><em>{</em><em>10</em><em>} = \frac{1}{f} \\ .. \\ f = </em><em>7</em><em>.</em><em>2</em><em>cm$

here positive sign indicates that...the focal length is on the left side of the lense....

......

...Image is also there...

..hope it helps u...

...THANKYOU...

..

..