PRELIMINARY STAGE 2013
Presbyterian Boys SHS
St Monicas
MfantsiMan Girls
ROUND 4 - TRUE OR FALSE
Longitudinal waves can be polarized.
ANSWER: FALSE
EXPLANATION:
Polarization restricts the oscillation direction perpendicular to propagation; longitudinal waves (e.g. sound) oscillate along the propagation direction and so cannot be polarized.
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PRACTICE QUESTIONS
1. QUESTION: Only transverse waves can be polarised.
ANSWER: TRUE
EXPLANATION:
Polarisation needs vibrations across the direction of travel.
2. QUESTION: Sound waves in air can be polarised.
ANSWER: FALSE
EXPLANATION:
Sound in air is longitudinal.
3. QUESTION: The polarisation of light shows that light is a transverse wave.
ANSWER: TRUE
EXPLANATION:
Longitudinal waves cannot be polarised.
4. QUESTION: Polarising sunglasses reduce glare from water.
ANSWER: TRUE
EXPLANATION:
Reflected light is partly polarised.
5. QUESTION: Radio waves cannot be polarised.
ANSWER: FALSE
EXPLANATION:
They are transverse; aerials must be lined up with them.
6. QUESTION: Light reflected from a water surface is partly polarised.
ANSWER: TRUE
EXPLANATION:
It is completely polarised at Brewster's angle.
7. QUESTION: In a longitudinal wave, the particles vibrate at right angles to the direction of travel.
ANSWER: FALSE
EXPLANATION:
They vibrate along the direction of travel.
8. QUESTION: Two crossed polarising filters block unpolarised light.
ANSWER: TRUE
EXPLANATION:
The second filter removes what the first lets through.
9. QUESTION: Polarising light changes its frequency.
ANSWER: FALSE
EXPLANATION:
Only the plane of vibration is restricted.