Dispersion

Q. A thin prism with angle of prism $A={10}^{\circ }$ has refractive index of $1.627$ for red light and $1.648$ for violet light. The angular dispersion produced by the prism will be :

1. ${0.37}^{\circ }$
2. ${0.0021}^{\circ }$
3. ${0.021}^{\circ }$
4. ${0.21}^{\circ }$