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IB Physics HL C 3 10 Reflection Refraction and Transmission At Boundaries Questions

Practise IB Physics HL C.3.10 by solving phase-change, thin-film thickness, reflected-wavelength and anti-reflection problems.

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • Determine reflected-ray phase changes and select constructive or destructive interference conditions.
  • Calculate film thickness or wavelength from thin-film path difference and refractive-index data.
  • Explain coloured fringes and anti-reflection coatings using reflected-wave interference.

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Study C.3.10—Reflection, refraction and transmission at boundaries conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics HL C 3 10 Reflection Refraction and Transmission At Boundaries Questions question 1

[Maximum number: 4]

Monochromatic light enters the base of a plastic beaker that contains water with an oil layer floating on it. A student draws a diagram to show the directions the light takes as it passes through the layers. The student's diagram has one error at position A and one error at position B. The refractive indices of the materials are shown on the diagram.

Figure for Question IB Physics HL C 3 10 Reflection Refraction and Transmission At Boundaries Questions question 1 — IB Physics HL

The light is refracted at an angle of 32∘32^{\circ} when it enters the plastic layer as shown.

Question (a)

(a)

Monochromatic light of wavelength 6.3×10−7 m6.3 \times 10^{-7} \mathrm{~m} in air is incident from above at a normal to the oil layer. Rays on the diagram are shown at near-normal incidence for clarity. Three positions X, Y and Z are shown on the diagram.

Figure for Question (a) — IB Physics HL
[ 4 ]

Question (i)

(i)

Identify, with a reason, a position at which there is a phase change of 180∘180^{\circ}.

[ 1 ]

Question (ii)

(ii)

Determine the minimum thickness of the oil layer for which light is not reflected. State your answer to an appropriate number of significant figures.

[ 3 ]
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