| Date | May 2014 | Marks available | 4 | Reference code | 14M.3.SL.TZ1.1 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain, Show that, Sketch, and State | Question number | 1 | Adapted from | N/A |
Question
This question is about diffraction and resolution.
Two identical sources of electromagnetic radiation, S1 and S2, emit monochromatic coherent waves of wavelength 59 μm. The waves pass through a circular aperture and are incident on a screen.
S1 and S2 are at the same distance from the aperture. The diameter of the aperture is 0.18 mm. The angle between the lines joining the sources to the aperture is 0.25 rad.
S1 is turned on and S2 is turned off.
(i) Show that the angle at which the first minimum of the diffraction pattern occurs is 0.40 rad.
(ii) On the axes below, sketch a graph to show how the intensity I of the radiation from S1 varies with the diffraction angle θ.
Markscheme
(i) \(\theta = \frac{{1.22 \times 59 \times {{10}^{ - 6}}}}{{0.18 \times {{10}^{ - 3}}}}\);
(=0.40rad)
(ii) central symmetrical maximum;
at least one secondary maximum on each side, no more than one third the height of the central maximum; (judge by eye)
minima drawn to zero, ie touching axis at θ=±0.40 (and ±0.80);
