Question

What is the focal length of 1.75 D reading glasses found on the rack in a pharmacy?

a) 0.571 mm
b) 0.625 mm
c) 0.550 mm
d) 0.600 mm

Answer 1

The focal length of 1.75 D reading glasses is 0.571 m. The confusion in the question options arises from units; the focal length should be expressed in meters, not millimeters.

Step-by-step explanation:

The question asks for the focal length of 1.75 D reading glasses found in a pharmacy. The focal length of 1.75 D reading glasses is 0.571 m. The confusion in the question options arises from units; the focal length should be expressed in meters, not millimeters.

To find the focal length in meters, we can use the formula:

focal length (m) = 1 / power (D)

So, for reading glasses with a power of 1.75 D, the focal length would be:

focal length = 1 / 1.75 D = 0.571 m

Hence, option (a) 0.571 mm is incorrect because the units should be in meters, not millimeters. The correct focal length, expressed in meters, is 0.571 m.