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Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: AN10 on March 21, 2010, 12:26:41 pm

Title: waves help
Post by: AN10 on March 21, 2010, 12:26:41 pm

plz solve question no 5 of first variant paper attached below

Title: Re: waves help
Post by: vanibharutham on March 21, 2010, 01:10:04 pm

For a wave to a have a minima, there must be destructive interference i.e. a phase difference of Pi radians...

However to detect a minima of ZERO, you must have a) A phase difference of Pi Radians b) Same Amplitude

Title: Re: waves help
Post by: AN10 on March 21, 2010, 01:32:10 pm

k i get it.... can u plz solve da second part too

Title: Re: waves help
Post by: AN10 on March 22, 2010, 10:49:38 am

anyone ??? ???

Title: Re: waves help
Post by: astarmathsandphysics on March 22, 2010, 11:37:20 am

I will do it when I get home in 1 hour

Title: Re: waves help
Post by: astarmathsandphysics on March 22, 2010, 12:32:45 pm

Distance frim S_2 to M is sqrt(1^2 +0,8^)=1.28m
so path difference =0.28m
when f=1kHz wavelength=v/f=330/1000=0.33
When f=4kHz wavelength=330/4000=0.0825
minumum whenw/2=28 or 3w/2 =28 or 5w/2=28 or 7w/2 =28
w=56 or w=18.7 or w=11.2 or w=8
only two of these are between 8.25 and 33
so only two minima

Title: Re: waves help
Post by: AN10 on March 22, 2010, 02:15:23 pm

ok....thanx a lot!!

Title: Re: waves help
Post by: halosh92 on March 27, 2010, 05:34:41 pm

Quote from: astarmathsandphysics on March 22, 2010, 12:32:45 pm

Distance frim S_2 to M is sqrt(1^2 +0,8^)=1.28m
so path difference =0.28m
when f=1kHz wavelength=v/f=330/1000=0.33
When f=4kHz wavelength=330/4000=0.0825
minumum whenw/2=28 or 3w/2 =28 or 5w/2=28 or 7w/2 =28
w=56 or w=18.7 or w=11.2 or w=8
only two of these are between 8.25 and 33
so only two minima

i dont get this part only:
minumum whenw/2=28 or 3w/2 =28 or 5w/2=28 or 7w/2 =28

Title: Re: waves help
Post by: astarmathsandphysics on March 27, 2010, 06:55:01 pm

w is the wavelenfth and mimima where paths difference  is w/2 or 3w/2 etc

Title: Re: waves help
Post by: astarmathsandphysics on March 27, 2010, 06:55:35 pm

cos that means destructive interference