Question

Find the focal length and nature of lens which should be placed in contact with a lens of focal length 10 cm so that the power of the combination becomes 5D.

Answer 1

power (P2) of length 10 cm focal length = 100/10=10D

let the power of the lens =P1

total powers of combination = P1+P2

5D=P1+100

P1=5D

focal length = -1/5 = -0.2 m

= -20 cm

power of the lens is negative so the given lens is concave lens

Answer 2

Answer:

Explanation:

REFER to the photos

IF U LIKE MY ANSWER. ... THEN MARK ME AS.'' BRAINLIEST '' ... PLZ. FRIEND