Question

$v_o$ and $V_E$ represent the velocities, ${\mu }_0$ and ${\mu }_E$ the refractive indices of ordinary and extraordinary rays for a double refraction crystal. Then

• A. $v_o⩾{\mu }_E,{\mu }_o⩽{\mu }_E,$ if the crystal is calcite.
• B. $v_o⩽{\mu }_E,{\mu }_o⩽{\mu }_E,$ if the crystal is quartz.
• C. $v_o⩽{\mu }_E,{\mu }_o⩾{\mu }_E,$ if the crystal is calcite
• D. $v_o⩾{\mu }_E,{\mu }_o⩾{\mu }_E,$ if the crystal is quartz.

Answer 1

The correct option is C $v_o⩽{\mu }_E,{\mu }_o⩾{\mu }_E,$ if the crystal is calcite

For an extra-ordinary ray in crystal calcite

$V_{ϵ}⩾v_0{v}_0=3\times {10}^{8}m/s$

${\mu }_E=\frac{V_{ϵ}}{V_0}⩾1B_y=1$

$M_0=\frac{V_0}{V_0}=1$

So ${\mu }_{ϵ}⩾M_0$

so option c. is correct