What Is the Angular Separation of Two Spectral Lines of Wavelengths

Multiple Choice

What is the angular separation of two spectral lines of wavelengths $497 \mathrm {~nm}$ and $251 \mathrm {~nm}$ formed in the third order with a diffracting grating having 587 lines per millimeter?

A) $34.8 ^ { \circ }$
B) $4.21 ^ { \circ }$
C) $29.4 ^ { \circ }$
D) $41.3 ^ { \circ }$
E) $24.8 ^ { \circ }$