Question 19M.2.HL.TZ1.3a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ1.3a |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | a | Adapted from | N/A |
A beam of microwaves is incident normally on a pair of identical narrow slits S1 and S2.
When a microwave receiver is initially placed at W which is equidistant from the slits, a maximum in intensity is observed. The receiver is then moved towards Z along a line parallel to the slits. Intensity maxima are observed at X and Y with one minimum between them. W, X and Y are consecutive maxima.
Explain why intensity maxima are observed at X and Y.
[2]
two waves superpose/mention of superposition/mention of «constructive» interference ✔
they arrive in phase/there is a path length difference of an integer number of wavelengths ✔
Many candidates were able to discuss the interference that is taking place in this question, but few were able to fully describe the path length difference. That said, the quality of responses on this type of question seems to have improved over the last few examination sessions with very few candidates simply discussing the crests and troughs of waves.
