A laser beam with a wavelength of 400 nm is directed at an angle of 20° to the normal diffraction grating. The grating has 3000 lines per mm. Determine the angles at which the first-order maxima occur. [Hint: d (sin Φ + sin θ) = ±m λ]

• A. The angles at which the first-order maxima occur are 46° and -46°.
• B. The angles at which the first-order maxima occur are 46° and -39°.
• C. The angles at which the first-order maxima occur are 79° and -46°.
• D. The angles at which the first-order maxima occur are 79° and -39°.