ChemISlife123
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https://papers.gceguide.com/A%20Leve..._w14_qp_11.pdf Q26

Why not C? Won't the amplitudes completely cancel out when they superpose?
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BobbJo
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You will hear successive soft sounds (minimum intensities) and loud sounds (maximum intensities). There will be no place where the sound intensity is exactly zero, because loudspeakers are not point sources of sound. Answers B and C cannot be correct.

The maxima gradually decrease in intensity away from the central maximum because the individual amplitudes of the two sound waves decrease with distance.

For a mininum, the path difference is (n+1/2)λ. One sound wave will have travelled a longer distance, so their amplitudes are not exactly the same. Complete destructive interference does not occur, so there still is a small amplitude (not zero)
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ChemISlife123
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Ohhh okay thanks but when it comes to light then the amplitudes will completely cancel right?
(Original post by BobbJo)
You will hear successive soft sounds (minimum intensities) and loud sounds (maximum intensities). There will be no place where the sound intensity is exactly zero, because loudspeakers are not point sources of sound. Answers B and C cannot be correct.

The maxima gradually decrease in intensity away from the central maximum because the individual amplitudes of the two sound waves decrease with distance.

For a mininum, the path difference is (n+1/2)λ. One sound wave will have travelled a longer distance, so their amplitudes are not exactly the same. Complete destructive interference does not occur, so there still is a small amplitude (not zero)
Last edited by ChemISlife123; 1 year ago
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BobbJo
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(Original post by ChemISlife123)
Ohhh okay thanks but how when it comes to light then the amplitudes will completely cancel right?
Yes [provided the source is small enough to act as a point source]
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ChemISlife123
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For example... a laser?
(Original post by BobbJo)
Yes, provided the source is small enough to act as a point source
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(Original post by ChemISlife123)
For example... a laser?
Yes. Also the intensity of light will not change much over the distance from the double slit to the screen. Light coming from the Sun reaches us with an appreciable intensity, and the Sun is found light years away from Earth. For sound its intensity decreases more noticeably
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ChemISlife123
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Ohhh okay thanks alot
(Original post by BobbJo)
Yes. Also the intensity of light will not change much over the distance from the double slit to the screen. Light coming from the Sun reaches us with an appreciable intensity, and the Sun is found light years away from Earth. For sound its intensity decreases more noticeably
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