Question

Magnification produced by a concave lens is always:
A. less than 1
B. more than 1
C. equal to 1
D. equal to 2

Answer 1

Hint: Magnification (m) of a lens is the power of the lens to magnify the image of an object. Magnification of lens is expressed in the ratio of the height of the image to the height of the object. Mathematically, \[m = \dfrac{Y}{X}\] where, Y is the height of the image and X is the height of the object.
If the height of the image produced by the lens is more than the height of the object, then the magnification of the lens is positive, and when the height of the image produced is less than the object height, then its magnification is negative.
In the question, it is asking about the magnification produced by a concave lens for which we need to know the properties of the concave lens.

Complete step by step solution:
A concave lens is a lens that has at least one curved surface inwards. When a light ray is projected on this lens the rays which refract through the curved surface spread out; hence it is a diverging lens.
When an object is kept in front of a concave mirror, it produces an upright, virtual and reduced in size image which is on the side of the object. As the image produced is reduced in size, hence the magnification produced is less than 1 as image height is less than the object height.
  \[{m_{concave}} < 1\]

Hence, Option A is correct.

Note: It is to be noted here that the magnification of the lens can also be negative when the image formed by the lens is inverted. If the height of the image formed by the lens is more than the actual (original) size of the object then, the magnification of a lens is more than 1 whereas the magnification is less than 1 if the height of the image formed by the lens is less than the actual (original) size of the object.