Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion-(A) : If Young's double slit experiment is performed in an optically denser medium than air, then the consecutive fringes come closer.
Reason-(R) : The speed of light reduces in an optically denser medium than air while its frequency does not change.
In the light of the above statements, choose the most appropriate answer from the options given below :
Solution
<p>We know, in YDSE,</p>
<p>$\beta$ (fringe width) $= {{\lambda D} \over d}$</p>
<p>In denser medium, $\lambda \downarrow \Rightarrow \beta \downarrow$</p>
<p>$\Rightarrow$ fringes come closer.</p>
<p>Also, $\mu = {c \over v} \Rightarrow v = {c \over \mu }$</p>
<p>$\Rightarrow \mu \uparrow \Rightarrow v \downarrow \Rightarrow$ speed of light reduces.</p>
<p>frequency remains same,</p>
<p>$$ \Rightarrow \mu = {{{\lambda _{vac.}}f} \over {{\lambda _{med.}}f}} \Rightarrow {\lambda _{med}} = {{{\lambda _{vac.}}} \over \mu }$$ (as $v = \lambda f$)</p>
<p>Hence, option C is correct.</p>
About this question
Subject: Physics · Chapter: Optics · Topic: Reflection and Mirrors
This question is part of PrepWiser's free JEE Main question bank. 197 more solved questions on Optics are available — start with the harder ones if your accuracy is >70%.