Question

How will the magnitude of magnification change if an object kept at infinity is moved towards focus of a convex lens?

• A. Decreases
• B. Increases
• C. Remains constant
• D. First decreases, then increases

Answer 1

The correct option is B Increases

As the object moves towards focus, the object distance from the pole of the lens decreases while the image distance increases. So as per the given formula, the height of image increases.
Since, magnification = $\frac{\text{height of image}}{\text{height of object}}$
Also, magnification = $\frac{imagedistance}{objectdistance}$

As height of image increases, magnitude of magnification increases.
As we are concerned about the magnitude only, so we need not pay attention to the sign of magnification.