Question

An opal acts like a reflection grating with rows separated by about 7 µm.

(a) If the opal is illuminated normally, what is the angle of smallest magnitude (in degrees, with respect to the rays of illuminating light) at which orange light will be seen? (Assume orange light has a wavelength of 590 nm.)

(b) If the opal is illuminated normally, what is the angle of smallest magnitude (in degrees, with respect to the rays of illuminating light) at which green light will be seen? (Assume green light has a wavelength of 510 nm.)

Answer 1

θ = Sin^-1 [ (1*590*10^-9) / (7*10^-6) ]

= Sin^-1 [ 0.08428 ]

θ = 4.83 ^o  --> Answer

b)

θ = Sin^-1 [ (1*510*10^-9) / (7*10^-6) ]

= Sin^-1 [ 0.07286 ]

θ = 4.18 ^o --> Answer