Question

The increase in size of optical image over the size of the object is known as
A. Limit of resolution
B. Transmission
C. Power of magnification
D. None of these

Answer 1

Hint: We are asked to choose the term from the given options whose definition is given in the question. For that, you could recall the definition of each of the given terms and then compare them to find the answer. Find the definition of these terms under the concept of optics. Recalling the definitions of every term makes you sure of your answer.

Complete answer:
We are asked to find the term that defines the increase in size of optical image over the size of the object from the terms given in the options. For that let us find out the definitions of each of the given terms.
First is the limit of resolution. Limit of resolution otherwise called resolving power is actually the measure of the ability of the lens to separate the image details such that we could distinctly observe very closely spaced objects.
Next is transmission. Transmission, optical transmission to be precise, is the measure of the proportion of light that can be transmitted through a turbid medium.
Now, we are left with the power of magnification that can be defined as the measure by which a lens can enlarge the image of an object.
Therefore, we find that the increase in size of optical image over the size of the object is known as power of magnification.

Hence, option C is the correct answer.

Note:
When we say power of magnification in optics, one shouldn’t confuse it with the optical power which is an entirely different quantity. Power of magnification is actually the ratio of apparent size of an object to that of its true size. That is, it is a dimensionless number. Also, magnifying an object cannot change the perspective of the image.