You would like to create a reflection grating like the one shown at the right, with an incident angle (θ) of 43 °. 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 -33 ° for visible light of 650 nm wavelength.

(b) A first order diffraction angle (Φ) of -33 ° for infrared light of 2.00 Ã- 10-3 cm wavelength.