Question

Relation between focal length and Power or lens having one side silvered
(with proper sign convention)

Please don't drive formula...explain me relation only.

as in case of lens p = 1/f but

in silvered lens we use
P = -1/f (why?)

EXPLAIN PROPERLY OTHERWISE REPORTED !​

Answer 1

$\huge\bigstar\underline\pink{Answer}$

★ Silvering of lens:-

★ For equiconvex lens, Plano-convex Lens and Plano-concave lens(where spherical part is silvered):-

P net = 2PL. + Pm

→ it means net power = twice the sum of power of lens + power of mirror.

[ As, you know Pm = -1/f]

so, net power = - 1/f

★ For plano-convex Lens (where plane part is silvered):-

→ Pm (power of mirror )=0

so, P net = 1/f

Happy to help!

☺️

Answer 2

Explanation:

Heya!

Silvering of lens:

1)For equiconvex lens, Plano-convex Lens and Plano-concave lens(where spherical part is silvered):-

P net = 2PL. + Pm

→ it means net power = twice the sum of power of lens + power of mirror.

[ As, you know Pm = -1/f]

so, net power = - 1/f

2)For plano-convex Lens (where plane part is silvered):

→ Pm (power of mirror )=0

so, P net = 1/f

Hope it helps!

:)