Question

The lens of a simple magnifier has a focal length of 2.5 cm. Calculate the angular magnification produced when (a) the image is at least distance of distinct vision, and (b) infinity.

• A. 11, 10
• B. 11, 13
• C. 10, 13
• D. 11, 12

Answer 1

The correct option is A 11, 10

Given: The lens of a simple magnifier has a focal length of 2.5 cm.

To find the angular magnification produced when (a) the image is at least distance of distinct vision, and (b) infinity.

Solution:

The simple magnifier achieves angular magnification by permitting the placement of the object closer to the eye than the eye could normally focus.

The angular magnification if the object is positioned such that the image is at least distant vision is given by the relationships below

$M_{\alpha }=\frac{25}{f}+1=\frac{25}{2.5}+1=11$

The angular magnification if the object is positioned such that the image is at infinity is given by the relationships below

$M_{\alpha }=\frac{25}{f}=\frac{25}{2.5}=10$