Question

Dispersive power of the material of a prism is $0.0221$. If the deviation produced by it for yellow colour is ${38}^o$, then the angular dispersion between red and violet colours is

• A. $0.65$ ${}^{\circ }$
• B. $0.84$ ${}^{\circ }$
• C. $0.48$ ${}^{\circ }$
• D. $1.26$ ${}^{\circ }$

Answer 1

Answer: (B)

$0.84$ ${}^{\circ }$

When light transitions from one medium into another medium, then it bends on the basis of the refractive indices of the two media. Dispersive power is the measurement of the amount of difference in the refraction of the highest and lowest wavelengths.

Formula for Dispersive power is given as:

Dispersive Power = $\frac{Angulardispersion}{meandeviation}$

Now, we will find the deviation for yellow color as the mean deviation,

$\omega =\frac{{\delta }_V-{\delta }_R}{{\delta }_Y}$

$0.0221=\frac{{\delta }_V-{\delta }_R}{{38}^{\circ }}$

${\delta }_{\nu }-{\delta }_R={0.84}^{\circ }$

Therefore angular dispersion between red and violet colors is ${0.84}^{\circ }$.

The correct option is B.