Q. 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 :
A) Both (A) and (R) are true but (R) is not the correct explanation of (A)
B) Both (A) and (R) are true and (R) is the correct explanation of (A)
C) (A) is true but (R) is false
D) (A) is false but (R) is true
Explanation
[Solution by Dr. Abubacker] In a denser medium $v$ decreases at constant $f$, so $\lambda=\frac vf$ decreases and the fringe width $\beta=\frac{\lambda D}{d}$ decreases. Both statements are true and (R) explains (A). Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.