Physics
Grade-10
Easy
Question
Salma wears a pair of eye lenses of focal length - 80 cm. What is the power of the lenses?
- +1.25 D
- +0.8 D
- -1.25 D
- -0.8 D
Hint:
Power is related to focal length. If focal length is negative power is also negative and vice versa.
The correct answer is: -1.25 D
The correct option is c)-1.25 D.
The focal length = -80cm
Power is the reciprocal of focal length but focal length should be in meters.
Focal length = -80/100 = -0.8m
Power= -1/0.8
Power = -1.25 D.
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