In the diagram shown, S is a source of light emitting plane polarized light with plane of polarization parallel to the plane of the figure having wavelength λ. M is a perfectly reflecting plane mirror. Intensity of light emitted by the source S is $$I0$$. If SM $$=$$ MP $$=$$ SP $$=$$ Nλ where N $$=$$ $$106$$, then intensity of light at P is

Question

In the diagram shown, S is a source of light emitting plane polarized light with plane of polarization parallel to the plane of the figure having wavelength λ. M is a perfectly reflecting plane mirror. Intensity of light emitted by the source S is $$I0$$. If SM $$=$$ MP $$=$$ SP $$=$$ Nλ where N $$=$$ $$106$$, then intensity of light at P is

Infinity Learn · Accepted Answer

Due to reflection at the mirror M, the reflected ray suffers an additional phase difference of $$180o$$ which is equivalent to a path difference of λ$$2$$. So total path difference at $$P=SM+MP$$−$$SP+$$λ$$2=106$$λ$$+$$λ$$2$$. Hence the waves interfering at P has a phase difference of $$180o$$. Therefore the angle between the electric fields at P is $$120o$$ as shown in the figure. ∴ $$ER=E0cos60o+E0cos60o=E0$$∴ $$IRI0=ERE02=1$$⇒$$IR=I0$$

Remember concepts with our Masterclasses.

Ready to Test Your Skills?

free study material