Question

The power of a lens is, - 2D. What is its focal length ?​

Answer 1

Explanation:

Power of lense =1/f

-2=1/f

f=-1/2

f = -0.5 or -50 cm

Answer 2

Given :-

• Power of a lens = - 2D

To find :-

• Focal Length

Solution :-

As we know that

→ Power = 1/focal length

→ p = 1/f

→ - 2 = 1/f

→ f = -1/2

→ f = - 0.5 m

Hence,

• Focal length is - 0.5 m
• - (minus) shows that it is a concave lens

Extra Information

• Power is denoted by P
• S.I unit of power is dioptre(D)
• It is the ability of lens to converge and diverge the ray of light falling on it.