Question

what is the focal length of the thin lens if the lens is in contact with 2.0 dioptre lens to form a combination lens which has a focal length of -80cm​

Answer 1

Answer:

i can't able to get answers

Answer 2

Answer: ≈ -37.75

Explanation:

Given power = 2.0 D

We know,

P = 1 / f

i.e, 2 = 1 / f1

⇒ f1 = 1 / 2 m

⇒ f1 = 50 cm

∴ One of the lenses' focal lengths (f1) is 50 cm.

We know,

1 / f2  = P2 - P1

⇒ 1 / f2 = ((-1) / 80) - (1 / 50)

⇒ 1 / f2 = (-5) - (8) / 400

⇒ 1 / f2 = (-13) / 400

⇒ f2 = - 400 / 13

⇒ f2 ≈ -30.75 cm

∴ The focal length of the other lens is -30.75 cm.