Physics
Classical Mechanics
Level
2
What is the power of a concave lens whose focal length is –75.0 cm ?
13.3 D
–13.3 D
1.33 D
–1.33 D
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1 solution
The focal length of a concave is negative and the equation Power = reciprocal of focal length and the unit of focal length should be in meters so − 7 5 / 1 0 0 = − . 7 5 M now by the above equation 1 / − . 7 5 = − 1 . 3 3 D (d stands for diopters)