Question

a convex lens of a convex lens of focal length 80 cm and a convex concave lens of focal length 50cm are combined together what will be their resulting power?​

Answer 1

Explanation:

Power of a lens is the ability of the lens to converge a beam of light falling on the lens it is measured as the reciprocal of focal length of the lens

i.e p = 1 / f ( in m )

When f is in cm,

P = 100 / f D

Here f1 = 80cm, f2 = -50cm

Combined power of two lenses in contact is given by Peq = P1 + P2

=> Peq = [ 1 / f1 ( m ) ] +[1 / f2( m ) ]

...[ f1 and f2 are with sign ]

=> P = ( 100 / 80 ) - ( 100/50 )

=> P = -0.75 D

∴ The Resulting Power will be

-0.75 D !

Answer 2

$Question:-$

♡ A convex lens of focal length 80 cm and a convex concave lens of focal length 50cm are combined together what will be their resulting power?​

$Given:-$

♡ f1 = 80 cm

♡ f2 = -50 cm

$To\:Find :-$

♡ Resulting power

$Answer:-$

♡ Power of combination (P) = P1 + P2

                                          $= \frac{100}{f1} + \frac{100}{f2}$

                                         $= \frac{100}{80} - \frac{100}{50}$

                                         = - 0.75 D

∴ The resulting power will be -0.75 D.