CourseCourseConceptConceptDocumentDocument

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

  • Explain why waves from two sources produce an interference pattern with intensity maxima and minima.
  • Connect light-sensor voltage peaks to constructive-interference maxima.
  • Calculate resultant amplitude from the path difference and individual wave amplitudes, including unequal amplitudes.
  • Identify intensity maxima and minima at different points by comparing their path differences with the wavelength.
  • Select a wavelength that gives destructive interference for a measured path difference.
  • Distinguish a phase difference of π radians from a half-wavelength path difference at a dark fringe.
  • Identify one fringe width in a ripple-tank interference pattern rather than a distance along wave propagation.
  • Sketch an ideal two-source intensity graph with equally spaced maxima and minima touching zero.
  • Read wavelength from successive intensity maxima when moving one source changes only that wave’s path length.
  • Predict how fringe separation changes when wavelength changes while the source geometry remains fixed.
  • Compare a first blue bright fringe with a first red dark fringe using their different interference conditions.
  • Predict the unchanged blue fringes, wider red fringes and colour coincidences when a second wavelength is added.
  • Count intensity maxima crossed when a microphone moves from a known destructive point toward an equidistant line.
  • Account for the source phase difference when predicting the signal along a line equidistant from both sources.
  • Explain why reflected sound can leave a faint signal at a position of destructive interference.
  • Explain how energy is redistributed toward interference maxima rather than lost at destructive minima.

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 .

All question bank results loaded