IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: Asamy111 on June 08, 2010, 03:00:41 pm

Title: phase difference and path difference
Post by: Asamy111 on June 08, 2010, 03:00:41 pm
hii .. can any1 plz write for me the exact formulas for path difference and phase difference cuz i don't hv it in the text book .. and explain it briefly plz
thnxxx
Title: Re: phase difference and path difference
Post by: nid404 on June 08, 2010, 03:02:20 pm
phase difference= (2\pi)/ (\lambda) X path difference

It's a set formula
Title: Re: phase difference and path difference
Post by: Meh on June 08, 2010, 03:03:54 pm
um. isn't phase difference (2 x pi x path difference) / lamda?
Title: Re: phase difference and path difference
Post by: Asamy111 on June 08, 2010, 03:06:58 pm
~Xena~ >> is it the same for both constructive and destructive ??
Title: Re: phase difference and path difference
Post by: nid404 on June 08, 2010, 03:08:23 pm
@meh-I've written the same thing  ::)

@assemy- yes..you use it for both. But the phase difference changes depending on the type of interference
Title: Re: phase difference and path difference
Post by: Asamy111 on June 08, 2010, 03:10:54 pm
thnxx alot ~Xena~
can u explain m/j 09 q5b varient 1 plz
cuz i don't gt from where i could find the no. of minima
Title: Re: phase difference and path difference
Post by: nid404 on June 08, 2010, 03:15:25 pm
Everyone on here has the same problem...I've solved this paper like a 100 times now... :P

I'll get you the link ...2 min  :)
Title: Re: phase difference and path difference
Post by: nid404 on June 08, 2010, 03:18:11 pm
phase difference=( 2pi/ lamda)  X path difference

phase difference = pi [ for destructive interference]
lambda(wavelength) = 2pi/ pi  X path difference.
path difference is S2M - S1M 
find S2M using Pythagoras = root of 802 + 1002
                                                   =128
path difference= 128-100=28
wavelength= 2pi/pi X 28
               =56cm                 
At f= 1KHz wavelength= 0.33m/ 33cm
At f=4kHz   wavelength= 0..0825/8.25cm
wavelength changes from 33cm to 8.25cm
for minima...phase difference should be either one of them pi, 3pi,5pi,7pi [sub them in the eqn]
minima is observed when lambda= 56cm, 18.7cm, 11.2cm, 8cm
which are the 2 values between 33 and 8.25?? 18.7 and 11.2...so only 2 minimas