When light of a certain wavelength is incident normally on a certain diffraction grating the line of order 1 is at a diffraction angle of 25 degrees. The diffraction angle of the second order line is :

Question

When light of a certain wavelength is incident normally on a certain diffraction grating the line of order 1 is at a diffraction angle of 25 degrees. The diffraction angle of the second order line is : 
a) 25 
b) 42 
c) 50 
d) 58 
e) 75

I am not sure how to do this problem since it does not have enough information to use the diffraction equations in the book. So, I do not know how to handle the problem.

Thank you

n lambda = d sin( theta ) 
Since the order n doubles from 1 to 2, so does the sine of the diffraction angle. Find the angle that has twice the sine of 25 degrees. It is not 50 degrees.

Dillon · Accepted Answer

d) 58 you said find the angle that is double sin25 (not sin50) so 2 x sin 25 gets you .84523 find what angle that is using inverse sin sin^-1 (.84523) = 57.697