| Date | May 2012 | Marks available | 1 | Reference code | 12M.3.SL.TZ2.3 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 3 | Adapted from | N/A |
Question
This question is about resolution.
Light from two monochromatic point sources passes through a circular aperture and is observed on a screen.
The graph shows how the intensity I of the light on the screen varies with the angle θ .
The two sources are just resolved according to the Rayleigh criterion.
State what is meant by resolved in this context.
The wavelength of the light from the two sources is 528 nm. The distance of the two sources from the aperture is 1.60 m.
Using data from the graph opposite, determine the
(i) separation of the two sources.
(ii) diameter of the aperture.
Markscheme
the two sources are seen as two distinct sources / two distinct images are formed / the central maximum of one source coincides with the first minimum of the other;
(i) realization that the diffraction angle of the one source diffraction pattern is at 0.008 radians;
and so separation (=1.60×0.008=1.28)≈0.013m;
(ii) \(\left( {1.22\frac{{528 \times {{10}^{ - 9}}}}{b} = 0.008 \Rightarrow } \right)b = 0.081{\rm{mm}}\);
Examiners report
