Question

Light is incident normally on a grating 0.25 cm wide with 1250 lines. Find the angular separation of the two sodium lines in the first order spectrum. Can they be seen distinctively if the lines are 5895 Å & 5901 Å.

Comments

The solution is wrong
Instead of 5000 there will be 1250.

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1250 per 0.25 cm

therefore

1250*4=5000 per 1 cm

The solution is correct

Answer 1

Data : Number of lines / cm (N)= 5000
m=1
λ1=5895 Å
λ2=5901 Å

Formula :

(a+b)sinθ=Nλ
mN=λ/dλ

Calculations :

---1

----2

---3

Number of lines / cm required for grating is 983
Number of lines / cm available for grating is 5000

angular separation is 0.0180
This lines will be resolved well by grating

Answer 2

Data : Number of lines / cm (N)= 5000
m=1
λ1=5895 Å
λ2=5901 Å

Formula :

(a+b)sinθ=Nλ
mN=λ/dλ

Calculations :