40. We use Eq. 37-22. For m =
±1
λ =
d sin θ
m
=
(1.73µm) sin(
±17.6
◦
)
±1
= 523 nm ,
and for m =
±2
λ =
(1.73µm) sin(
±37.3
◦
)
±2
= 524 nm .
Similarly,we may compute the values of λ corresponding to the angles for m =
±3 . The average value
of these λ
s is 523 nm.