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VICPhysicsQuick questions
Unit 4: How have new ideas and ways of thinking developed our understanding of the physical world?
Quick questions on Wave model of light and interference: VCE Physics Unit 4
9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is setup?Show answer
Monochromatic (single-wavelength), coherent light passes through two narrow slits separated by distance . The light reaching the screen at distance from the slits is the superposition of two waves, one from each slit.
What is coherence requirement?Show answer
The two sources must have a fixed phase relationship. In practice, both slits are illuminated by the same monochromatic source (e.g., a laser, or a single slit illuminated first), ensuring coherence.
What is observation?Show answer
A regular pattern of bright and dark fringes appears on the screen. Bright fringes correspond to constructive interference (the waves arrive in phase); dark fringes correspond to destructive interference (the waves arrive out of phase by ).
What is pattern?Show answer
A central bright band, flanked by progressively dimmer side bands separated by dark fringes. The central band is twice as wide as the side bands.
What is dark fringe condition?Show answer
Dark minima occur at angles where:
What is width of the central maximum?Show answer
From the first dark fringes on either side: , so the angular half-width is . The angular full-width is .
What is q1?Show answer
State the formula for fringe spacing in a Young's double-slit experiment, with each symbol defined. [2 marks]
What is q2?Show answer
A double-slit experiment with mm and m produces fringes mm apart. Calculate the wavelength. [3 marks]
What is q3?Show answer
Refer to the Melbourne University HeNe demonstration. (a) Calculate fringe spacing for nm, mm, m. (b) Determine the wavelength if a green laser produces mm fringes.