| Date | November 2009 | Marks available | 1 | Reference code | 09N.1.HL.TZ0.19 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Question number | 19 | Adapted from | N/A |
Question
Two galaxies with an angular separation at the observer of \(5.0 \times {10^{ - 4}}\) radians are observed with a radio telescope. Both galaxies emit radio waves of wavelength \(2.5 \times {10^{ - 2}}{\text{ m}}\).
The images of the galaxies are just resolved by the telescope. The diameter of the circular collecting dish of the telescope is
A. 61 m.
B. 50 m.
C. 30 m.
D. 25 m.
Markscheme
A
Examiners report
Students need to be aware of the factor of 1.22 used for circular lenses.
