CE PHY 2007 PAPER1 10B

用戶24503

2009-04-07 5:40 am

http://img.photobucket.com/albums/v225/cpwing/1111.jpg

why the path difference between PY and QY is 2 x wavelength?

only because there are 5 maximum sound between BY?

詳細解釋 thanks....

更新1:

is that means the wavelength is not the original wavelength of the signal? the wavelength is from the wave in CRO trace?

回答 (1)

天同

2009-04-07 6:07 am

✔ 最佳答案

From the CRO trace, there is no path difference at B, because it is just opposite A, the mid point between the two speakers.
Hence, at X, there is a path difference of (1/2) wavelength, because the distaance from crest to trough is half a wavelength.
At the next trough at the right side of X, there is a path difference of (1/2) + 1 = 1-1/2 wavelength. It is because the distance from trough to trough is a wavelength.
Therefore, at Y, there is a path difference of (1-1/2)+(1/2) = 2 wavelengths.

2009-04-06 22:08:32 補充：
note: [1-1/2] denotes "one and a half"

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