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IB Physics SL C 3 8 Two Source Interference Questions

Practise IB Physics SL C.3.8 by predicting two-source interference patterns and explaining how wavelength, spacing and path difference change them.

Syllabus
First assessment 2025
Course
Physics SL
Level
SL

Exam points

  • Predict bright and dark regions from two-source path difference and wavelength.
  • Explain how changing wavelength, source spacing or screen geometry changes fringe spacing.
  • Interpret interference patterns for light, sound or water waves using phase and path information.

Learn this topic

Study C.3.8—Two-source interference conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics SL C 3 8 Two Source Interference Questions question 1

[Maximum number: 1]

This question is about interference.

Light from a laser is incident on two identical parallel slits. The light from the two slits produces a fringe pattern on a screen.

Figure for Question IB Physics SL C 3 8 Two Source Interference Questions question 1 — IB Physics SL

A central bright fringe is produced at C . The next bright fringe is produced at A . There is a dark fringe at B .

State the phase difference between the light waves from the two slits that meet at B .

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