Question

two thin lenses o focal lengths 10 cm and 20 cm respectively are placed in contact. the effective power of combination o lens is

Answer 1

QUESTION:

two thin lenses o focal lengths 10 cm and 20 cm respectively are placed in contact. the effective power of combination o lens is.

ANSWER:

GIVEN:

Two thin lenses focal length = 10 cm and 20 cm.

WE add both the focal length.

$10cm + 20cm \\ 30cm$

To find the power we use the formula :

$power = \frac{1}{f(m)} \\ where \\ f = focal \: length$

30 cm in metre.

30/100 m.

3/10 m.

$p = \frac{1}{ \frac{3}{10} } \\ p = \frac{10}{3} d$

power = 10/3 Dioptre.

PLZ MARK AS BRAINLIEST

Answer 2

Answer:

15 D

Explanation:

$p \: = \: p1 + p2$

$p1 = \frac{100 \: (in \: cm)}{f} \: \\ = > \: \frac{100}{10} = 10d$

$p2 = \frac{100}{20} = 5d$

p = 10 D + 5D

P = 15 D

hope it helps you