Question 19M.2.HL.TZ1.b
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.HL.TZ1.b |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Determine | Question number | b | 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.
The distance from S1 to Y is 1.243 m and the distance from S2 to Y is 1.181 m.
Determine the frequency of the microwaves.
[3]
path difference = 0.062 «m»✔
so wavelength = 0.031 «m»✔
frequency = 9.7 × 109 «Hz»✔
Award [2 max] for 4.8 x 109 Hz.
Many candidates struggled with this question. Few were able to calculate a proper path length difference, and then use that to calculate the wavelength and frequency. Many candidates went down blind paths of trying various equations from the data booklet, and some seemed to believe that the wavelength is just the reciprocal of the frequency.
