Question 21M.2.HL.TZ1.6
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.HL.TZ1.6 |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Calculate, Explain, State | Question number | 6 | Adapted from | N/A |
A painting is protected behind a transparent glass sheet of refractive index nglass. A coating of thickness w is added to the glass sheet to reduce reflection. The refractive index of the coating ncoating is such that nglass > ncoating > 1.
The diagram illustrates rays normally incident on the coating. Incident angles on the diagram are drawn away from the normal for clarity.
State the phase change when a ray is reflected at B.
[1]
✓
Explain the condition for w that eliminates reflection for a particular light wavelength in air .
[3]
«to eliminate reflection» destructive interference is required ✓
phase change is the same at both boundaries / no relative phase change due to reflections ✓
therefore
OR
OR
✓
State the Rayleigh criterion for resolution.
[1]
central maximum of one diffraction pattern lies over the central/first minimum of the other diffraction pattern ✓
The painting contains a pattern of red dots with a spacing of 3 mm. Assume the wavelength of red light is 700 nm. The average diameter of the pupil of a human eye is 4 mm. Calculate the maximum possible distance at which these red dots are distinguished.
[2]
✓
✓