DP Physics (last assessment 2024)
Question 19M.1.HL.TZ1.31
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.1.HL.TZ1.31 |
| Level | HL | Paper | 1 | Time zone | TZ1 |
| Command term | Question number | 31 | Adapted from | N/A |
31.
[Maximum mark: 1]
19M.1.HL.TZ1.31
A transparent liquid film of refractive index 1.5 coats the outside of a glass lens of higher refractive index. The liquid film is used to eliminate reflection from the lens at wavelength λ in air.
What is the minimum thickness of the liquid film coating and the phase change at the liquid–glass interface?
[1]
Markscheme
D
Examiners report
Half of candidates (incorrectly) selected response B, suggesting that while they recognized the phase change of π, determining the minimum thickness of the thin film was challenging. The discrimination index was very low for this question.
