A Parallel Beam of Sodium Light of Wavelength 589 Nm $\times$

Multiple Choice

A parallel beam of sodium light of wavelength 589 nm is normally incident on a diffraction grating.If the second order diffraction maximum is observed at 50.25 degrees to the normal,then calculate the number of lines per cm of the grating.

A) 5.69 $\times$ 10⁵ cm^-1
B) 1.53 $\times$ 10⁶ cm^-1
C) 6.53 $\times$ 10³ cm^-1
D) 1.31 $\times$ 10⁶ cm^-1
E) 1.31 $\times$ 10⁴ cm^-1