Question

Two lenses have power of +2D and -6D respectively. Calculate the focal length of the combination​

Answer 1

Answer:

-4D

Explanation:

bhais milne ki ummid nahi thi ki

Answer 2

Answer:

Power P1 = 2D;

 Since Power is positive. Therefore, the lens is convex lens.  

Power = 1/focal length (in meters)

⇒ 2 = 1/f

 ⇒ f = 1/2 = 0.5m

1m = 100cm

 ⇒ 0.5m = 50cm.

Hence the focal length is 50cm

 P2 = -4D.  

Since the power is negative. Therefore, the lens is concave lens.

Power = 1/focal length (in meters)

⇒ -4f = 1/f

⇒ f = 1/−4 = -0.25m

1m = 100cm

 ⇒ 0.25m = 25cm.  

Hence the focal length is -25cm