(i) State and exp

It is essentially based on geometric constructions which allows us to determine the shape of the wavefront anytime., if the shape of the wavefront at earlier is known.

(ii) We know that, energy expression of any wave is,

Now, for refraction, frequency doesn’t change, so energy will also remain constant.

OR

Magnification power,

Multiplying and dividing by I₁G₁,

(m_e=magnification of eye piece, m_o=magnification of objective)

Now, and

The magnification power can be increased by using an eye piece of less focal length.