Question

A parallel beam of sodium light is incident normally on a diffraction grating. The angle between the two first order spectra on either side of normal is 27 degree 42 minute . Assuming that the wavelength of light is 5.893* 10^-7 m. Find the number of rulings per mm on the grating.

Answer 1

And how does that figure give the solution?

Answer 2

we have relation, \( d \sin\theta = n \lamda \)

Answer 3

for first order, n=1, since \( \theta\) is given, we can calculate d, but i don't understand why two results are given.

Answer 4

and what do we do with d? well the answer is 406 per mm.

Answer 5

http://www.wolframalpha.com/input/?i=1%2F%285.893*+10%5E-4%2Fsin%2827+degree+42+minute%29%29
Guess it didn't work.

Answer 6

d can't have that greater value..

Answer 7

procedure seems all right
http://www.physics.smu.edu/~scalise/emmanual/diffraction/lab.html

Answer 8

there was a calculation error earlier. And i think 27 degree and 42 min should be divided by 2 to get actual value of theta.. since the angle given in question is the angle between TWO first order spectra.. the calculations then made by me gives a value of 2.46*10^-6 for d. suppose i am correct. what next?

Answer 9

d is the distance between two adjacent grating lines, change d into mm and divide 1 by this value.

Answer 10

decreasing value of angel gives crazy data.

Answer 11

http://www.wolframalpha.com/input/?i=1%2F+%285.893*+10%5E-4+%2F+sin%2827.7%2F2%29%29

Answer 12

thanks! i got the answer!!

Answer 13

how??

Answer 14

the same formula. divided the angle given in question by 2 so, theta= 13 degree 51 min, lambda is given, n=1.. that makes d=2.46*10^-6 m. converted this value into mm.. and the reciprocal of then obtained value was the answer.. you made calculations mistake earlier. however, formula was useful. thanks buddy!

Answer 15

haha .. sure you are welcome.