Question 160: Waves Optics

Question

A plane polarized light is incident on a polariser with its pass axis aking angle $$	heta $$ with x-axis, as shown in the figure.  At four different values of $$	heta ,\,	heta $$ = 8o, 38o, 188o and 218o, the observed intensities are same. 
What is the angle between the direction of polarization and x-axis ?

Accepted Answer

According to Malus law, we have
$$I = {I_0}{\cos ^2}	heta  \Rightarrow {I \over {{I_0}}} = {\cos ^2}	heta $$
Since the observed intensities are same for all values of $$	heta$$, therefore, for the angles given in options, the observed intensity should be same as well for all $$	heta$$, $$	heta$$ = 8$$^\circ$$, 38$$^\circ$$, 188$$^\circ$$ and 218$$^\circ$$, $${I \over {{I_0}}} \sim 0.9$$; and for $$	heta$$ = 203$$^\circ$$, $${I \over I} \sim 0.9$$.
Therefore, angle between direction of polarisation and x axis is 203$$^\circ$$.

Answer

98o

Answer

128o

Answer

203o

Answer

45o

Waves Optics

Choose the correct answer: