48.
(a) We find ∆λ from R = λ/∆λ = N m:
∆λ =
λ
N m
=
500 nm
(600/mm)(5.0 mm)(3)
= 0.056 nm = 56 pm .
(b) Since sin θ = m
max
λ/d < 1,
m
max
<
d
λ
=
1
(600/mm)(500
× 10
−6
mm)
= 3.3 .
Therefore, m
max
= 3. No higher orders of maxima can be seen.