A magnifying lens with a focal length of 20 cm has what magnification when the viewing eye is relaxed?
A)7.14
B)1.3
C)1.8
D)2.3

Question

Quizplus · Accepted Answer

The magnification given by a magnifying lens is given by the formula: 
magnification = 1 + (focal length of lens / distance of object from lens)
When the viewing eye is relaxed, the lens is held at a distance of 25 cm from the eye (the far point) and the object being viewed is also at a distance of 25 cm from the eye. 
Substituting these values into the formula: 
magnification = 1 + (20 cm / 25 cm) = 1.8 
Therefore, the correct answer is B) 1.3.

A Magnifying Lens with a Focal Length of 20 Cm