hi would please help me in answering this question and plesa while answering explain how u progressed to this result
the paper is may/june CIE physics 2009
question 5 part b)
here u go
there is a formula u need to know
phase difference=( 2pi/ lamda) X path difference
phase difference = pi [ for destructive interference]
lambda(wavelength) = 2pi/ pi X path difference.
path difference is S
2M - S
1M
find S
2M using Pythagoras = root of 80
2 + 100
2 =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