Question

$v_{o}$ and $v_{E}$ represent the velocities, $\mu_{o}$ and $\mu_{E}$ the refractive indices of ordinary and extraordinary rays for a doubly refracting crystal. Then

• A. $v_{o} \geq v_{E}, \mu_{o} \leq \mu_{E}$ if the crystal is calcite
• B. $v_{o} \leq v_{E}, \mu_{o} \leq \mu_{E}$ if the crystal is quartz
• C. $v_{o} \leq v_{E}, \mu_{o} \geq \mu_{E}$ if the crystal is calcite
• D. $v_{o} \geq v_{E}, \mu_{o} \geq \mu_{E}$ if the crystal is quartz

Answer 1

Answer: (C)

In double refraction light rays always splits into two rays $(O$ -ray and $E$ -ray $) . O$ -ray has same velocity in all direction but $E$ -ray has different velocity in different direction.
For calcite $\mu_{e} < \mu_{0} \Rightarrow v_{e} > v_{0}$
For quartz $\mu_{e} > \mu_{0} \Rightarrow v_{0} > v_{e}$