Polarisation as Evidence for Transverse Waves · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Polarised light proves waves go sideways

Science · Waves, Light & Sound · ages 16-17
Name ______________________   Date ____________

  1. Two crossed filters at 90 degrees block the light fully.

    Circle one:   True   False

  2. Which waves can be polarised?

    • Transverse only
    • Longitudinal only
    • All waves equally

  3. Two filters are aligned. What happens to the light?

    • Light is fully blocked
    • Light passes
    • Light doubles in brightness

  4. The two-filter test is tried on sound. What does the result show?

    • Sound cannot be polarised, so it is longitudinal
    • Sound polarises better than light
    • Sound is transverse

  5. Why do polarising sunglasses cut glare from water?

    • The lens adds extra light to wash it out
    • Glass stops being transverse behind lenses
    • Reflected glare is partly polarised, so the lens blocks that direction

  6. A TV aerial works best turned to one angle. Why?

    • Only the matching alignment gets through strongly
    • Aerials attract more electrons sideways
    • Angles change the broadcast colour

  7. Unpolarised sunlight meets one filter. What comes out?

    • Unpolarised light stays unchanged
    • Light polarised along the filter axis
    • No light at all

  8. A pupil claims to have polarised sound in an experiment. What should you conclude?

    • The sound turned transverse in air
    • The filters were aligned by luck
    • The claim is wrong: longitudinal waves cannot be polarised
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Polarised light proves waves go sideways W1-mt_mCbxv77qDA-s1

  1. True · Nothing of the first direction fits the second slit.
  2. Transverse only · Polarisation needs sideways oscillations, which only transverse waves have.
  3. Light passes · Matching slits let the same direction straight through.
  4. Sound cannot be polarised, so it is longitudinal · No change under rotation means no polarisation, hence longitudinal.
  5. Reflected glare is partly polarised, so the lens blocks that direction · Glare vibrates mostly one way, and the lens is set against it.
  6. Only the matching alignment gets through strongly · The aerial must match the signal's polarisation to catch it.
  7. Light polarised along the filter axis · The filter keeps one direction from the mix and drops the rest.
  8. The claim is wrong: longitudinal waves cannot be polarised · Sound oscillates along its travel, so no filter direction can select it.
Worksheet · LightMySky