The slit-width-to-wavelength ratio for 30 degrees will be 2; for 60 degrees will be 0.87, and lastly, for 90 degrees angles will be 1.
The computation of slit-width-to-wavelength ratio for each of the angles after assuming that the small-angle approximation as invalid, has been given, as below,
sin θ = λ / a
sin30∘ = λ / a
0.5 = λ / a
a / λ = 2
Similarly,
sin θ = λ / a
sin60∘ = λ / a
0.87 = λ / a
a / λ = 0.87
And lastly, for 90 degrees
sin θ = λ / a
sin90∘ = λ / a
1 = λ / a
a / λ = 1
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