Question:
The focal length of a concave lens is 0.5 m. The power of the lens is
The focal length of a concave lens is 0.5 m. The power of the lens is
Options:
- +0.5 D
- –0.5 D
- +2.0 D
- –2.0 D
- +0.5 D
- –0.5 D
- +2.0 D
- –2.0 D
Correct Answer: –2.0 D
Explanation:
P = 1 / f = 1 / -0.5 = -2 D. -ve sign as focal length if concave is negative.
P = 1 / f = 1 / -0.5 = -2 D. -ve sign as focal length if concave is negative.