angular width is 0.10 degree
Explanation:
Given data
width = 340 nm
separation d = 790 nm
λ = 520 nm
to find out
how many maxima and width of a spectral line
solution
we know for maxima formula is
m λ = dsinθ
and we know here sinθ is between 0 and 1
so we can say
d is greater than m λ
and
m ≤ d / λ
m ≤ 790 / 520
m ≤ 1.52
its mean we have 3 maxima i.e. 0 , 1 and -1
and
for 1st order m = 1
so mλ = dsinθ
λ = dsinθ
θ = sin^-1 ( λ/d) ................................1
and angular width is
θ = λ/ Nd cosθ
θ = dsinθ / Nd cosθ
θ = tanθ /N ...............................2
so here put θ in 2 equation
angular width = tanθ/N
angular width = tan ( sin^-1 ( 520/790) ) / 500
angular width = tan 41.16 / 500
angular width = 1.7484 × × 180/π
angular width = 0.10 degree