A person's left eye is corrected...

Question

A person's left eye is corrected by a -5.0 diopter lens, 2.01 cm from the eye. What is this person's far point without glasses? Give an answer in cm.

Answer: 2.20E1 (2.20 × 101)

I can't seem to figure how to get to the answer above. I would appreciate your help.

Answer 1

The focal length of a lens with a power of -5. P=-5=1/f  Unit of f in meters.

So, f=-1/5=-.2 m or 20 cm.

Far point without glasses = 20 cm + 2.01 cm = 22.01 cm or in scientific notation 2.201exponential 1 = 2.201 x 10^1 = 22.01 cm.

Answer 2

P=-5 diopters means that the focal length  f = -20 cm

Its a diverging lens.