(i) State and explain Huygens Principle. Using it, obtain Snell’s law of refraction.
(ii) When light travels from a rarer to a denser medium, the speed decreases. Does the reduction in speed imply a reduction in the energy carried by the light wave?

OR

With the help of a labeled ray diagram show the image formation by a compound microscope. Derive an expression for its magnifying power. How can the magnifying power be increased?

Question

(i) State and explain Huygens Principle. Using it, obtain Snell’s law of refraction.
(ii) When light travels from a rarer to a denser medium, the speed decreases. Does the reduction in speed imply a reduction in the energy carried by the light wave?

OR

With the help of a labeled ray diagram show the image formation by a compound microscope. Derive an expression for its magnifying power. How can the magnifying power be increased?

Philoid · Accepted Answer

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.