Problem- You would like to create a reflection grating like the one shown at the right, with an incident angle (θ) of 49 °. Calculate the number of lines per centimeter that should be etched in the grating for each of the following conditions:
(a) A first order diffraction angle (Φ) of -23 ° for visible light of 400 nm wavelength.
(b) A first order diffraction angle (Φ) of -23 ° for infrared light of 4.00 x 10^-3 cm wavelength.
Please define why you think that's the right answer