| Date | May 2011 | Marks available | 1 | Reference code | 11M.3.SL.TZ1.21 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | State | Question number | 21 | Adapted from | N/A |
Question
This question is about using a diffraction grating to view the emission spectrum of sodium.
Light from a sodium discharge tube is incident normally upon a diffraction grating having 8.00×105 lines per metre. The spectrum contains a double yellow line of wavelengths 589 nm and 590 nm.
Determine the angular separation of the two lines when viewed in the second order spectrum.
[4]
a.
State why it is more difficult to observe the double yellow line when viewed in the first order spectrum.
[1]
b.
Markscheme
d=18.00×105=1.25×10−6m;
dsinθ=nλ⇒θsin−1[nλd];
sin−1[2×589×10−91.25×10−6]=70.5∘,sin−1[2×590×10−91.25×10−6]=70.7∘;
70.7°−70.5°=0.2°;
a.
the lines are closer together / not clearly separate in the first order spectrum;
b.
Examiners report
[N/A]
a.
[N/A]
b.
