19th NOV 2013 test  study group
19th NOV 2013 test  study group
hi
anyone here taking the Pgre test this 19th of November  if so please stand up. We could discuss and study together
how important is Pgre score in selecting a candidate for a PhD program (I am already in my last semester of MS Physics)
is a score of 750 decent  how many questions do i have to get correct to obtain 750?
anyone here taking the Pgre test this 19th of November  if so please stand up. We could discuss and study together
how important is Pgre score in selecting a candidate for a PhD program (I am already in my last semester of MS Physics)
is a score of 750 decent  how many questions do i have to get correct to obtain 750?
Re: 19th NOV 2013 test  study group
delsub wrote:hi
anyone here taking the Pgre test this 19th of November  if so please stand up. We could discuss and study together
how important is Pgre score in selecting a candidate for a PhD program (I am already in my last semester of MS Physics)
is a score of 750 decent  how many questions do i have to get correct to obtain 750?
I think you mean 19th of October. There's no PGRE this year in November.
Re: 19th NOV 2013 test  study group
yes october. lol
Re: 19th NOV 2013 test  study group
hey can someone pls explain this problem to me 
http://grephysics.net/ans/8677/12
why isnt the answer = D ==> 1.9 khz
I used the following equation >
F'= F (V+Vs)/(V+Vo)
Here V = velocity of sound
Vs = velocity of source, taken positive if it is moving in the direction of the sound (i.e from the S to the O)
Vo = Velocity of observer, taken positive if it is moving in the direction of the sound.
Is something wrong with the equation
http://grephysics.net/ans/8677/12
why isnt the answer = D ==> 1.9 khz
I used the following equation >
F'= F (V+Vs)/(V+Vo)
Here V = velocity of sound
Vs = velocity of source, taken positive if it is moving in the direction of the sound (i.e from the S to the O)
Vo = Velocity of observer, taken positive if it is moving in the direction of the sound.
Is something wrong with the equation

 Posts: 14
 Joined: Sun Sep 29, 2013 12:07 pm
Re: 19th NOV 2013 test  study group
I think, the equation isdelsub wrote: I used the following equation >
F'= F (V+Vs)/(V+Vo)
Here V = velocity of sound
Vs = velocity of source, taken positive if it is moving in the direction of the sound (i.e from the S to the O)
Vo = Velocity of observer, taken positive if it is moving in the direction of the sound.
F' = F * [(V+Vo)/(V+Vs)]
http://en.wikipedia.org/wiki/Doppler_effect
Re: 19th NOV 2013 test  study group
here is another i dont get at all 
http://grephysics.net/ans/8677/44
since the collision is elastic the KE is preserved.
so 1/2 mv^2 = 1/2 MV^2
or V = v(m/M)^1/2
so why are they saying answer is A
http://grephysics.net/ans/8677/44
since the collision is elastic the KE is preserved.
so 1/2 mv^2 = 1/2 MV^2
or V = v(m/M)^1/2
so why are they saying answer is A
Re: 19th NOV 2013 test  study group
no their convention of whats positive and whats negative velocity is different.MomSaysImSpecial wrote:I think, the equation isdelsub wrote: I used the following equation >
F'= F (V+Vs)/(V+Vo)
Here V = velocity of sound
Vs = velocity of source, taken positive if it is moving in the direction of the sound (i.e from the S to the O)
Vo = Velocity of observer, taken positive if it is moving in the direction of the sound.
F' = F * [(V+Vo)/(V+Vs)]
http://en.wikipedia.org/wiki/Doppler_effect
In my convention, all velocities along the direction of the wave  i.e from S to O is positive and opposite it is ve.
So when S moves towards the O, Vs adds to V upstairs  to give a greater F
When S moves away from 0  i.e in the direction opposite to S>O, the Vs subtracts from V upstairs, to give a lower F.
Similarly with O 
so why is my equation not working ??

 Posts: 14
 Joined: Sun Sep 29, 2013 12:07 pm
Re: 19th NOV 2013 test  study group
Let's try to derive it together.delsub wrote:so why is my equation not working ??
When the observer doesn't have any speed in the medium, he can receive the signals of the circular frequency:
Omega = 2pi* (c/lambda)
Here 'c' is the speed of sound waves and 'lambda' is the wavelength of the 'new' wave. If we take into account the velocity of the source in the medium, we can see that:
lambda = 2pi*(cv)/Omega0
'Omega0' is the original frequency of the source.
'v' is the speed of source with respect to the medium. Positive when (O<S, the received wavelength is shorter since source is 'chasing' the original signal) and negative when (O S>, the received wavelength is longer). Thus, we have:
Omega = Omega0/(1  v/c)
We can also consider the case when the observer is moving and then get the general equation, but it is enough for our problem.
Re: 19th NOV 2013 test  study group
Thanks a lot. That solves it
I have another doubt or rather a set of doubts  i am getting confused every time i study it . can someone please help  with optics
What are the formula for MAXIMA in the following  I have filled up the ones I know (0= theta and L = lambda)  Please correct/complete
Slab of material > nt = (m+.5)n' L
Thin film interference> 2nt = (m + .5) L
Young's Double slit Interference> d sin 0 = (m+.5) L
Single slit Interference >
Diffraction Grating > 2d Sin0 = m L
Bragg Diffraction
Raleigh Criteria/Aperture formula
I have another doubt or rather a set of doubts  i am getting confused every time i study it . can someone please help  with optics
What are the formula for MAXIMA in the following  I have filled up the ones I know (0= theta and L = lambda)  Please correct/complete
Slab of material > nt = (m+.5)n' L
Thin film interference> 2nt = (m + .5) L
Young's Double slit Interference> d sin 0 = (m+.5) L
Single slit Interference >
Diffraction Grating > 2d Sin0 = m L
Bragg Diffraction
Raleigh Criteria/Aperture formula
Re: 19th NOV 2013 test  study group
Photoelectric effect Photon knocks out e1. In Compton effect e1 knocks out the photon
Stern Gerlach experiment Spin gerlach exp Neutral atoms 2S + 1 due to spin
Frank Hertz experiment Electrons can be scattered elastically and Energy lost is discrete
Stark effect
Zeeman effect
Anomalous Zeeman effect
Hall effect To find positive or negative charge
Michelson Morley exp
Michael’s interferometer
Bohr postulate
Fine structure Spin orbit coupling
Lamb shift
Born Oppenheimer approx WF molecule = WF nucleus X WF electron
Born approximation In perturbation theory
Born assumption Psi square psi = probability
Fermi’s golden rule Perturbation – prob of transition from one Eigen state to a band of Eigen
Pauli’s exclusion principle Anti symmetric wave function
Pair production Particle and anti particle production
Auger transition Particle knocks inner electron out. Outer e1 fills in + release of energy
Internal conversion An orbital electron is absorbed by nucleus and ejected along with an Xray.
Gamma Ray Production The excited nucleus jumps to a lower level and emits a photon .
Photoelectric effect
Compton effect
Band spectra
Lamour precession
Lamour formula
Bremsterlung
Auger transition Particle knocks inner electron out. Outer e1 fills in + release of energy
Cherenkov radiation
Synchrotron radiation
Cyclotron motion
Lamb shift
Fourier’s law
Malus law
Meyer’s eq
Brewster’s law
Brewster’s angle
Delong Petit law
Critical isotherm
Liquid vapor region
Stern Gerlach experiment Spin gerlach exp Neutral atoms 2S + 1 due to spin
Frank Hertz experiment Electrons can be scattered elastically and Energy lost is discrete
Stark effect
Zeeman effect
Anomalous Zeeman effect
Hall effect To find positive or negative charge
Michelson Morley exp
Michael’s interferometer
Bohr postulate
Fine structure Spin orbit coupling
Lamb shift
Born Oppenheimer approx WF molecule = WF nucleus X WF electron
Born approximation In perturbation theory
Born assumption Psi square psi = probability
Fermi’s golden rule Perturbation – prob of transition from one Eigen state to a band of Eigen
Pauli’s exclusion principle Anti symmetric wave function
Pair production Particle and anti particle production
Auger transition Particle knocks inner electron out. Outer e1 fills in + release of energy
Internal conversion An orbital electron is absorbed by nucleus and ejected along with an Xray.
Gamma Ray Production The excited nucleus jumps to a lower level and emits a photon .
Photoelectric effect
Compton effect
Band spectra
Lamour precession
Lamour formula
Bremsterlung
Auger transition Particle knocks inner electron out. Outer e1 fills in + release of energy
Cherenkov radiation
Synchrotron radiation
Cyclotron motion
Lamb shift
Fourier’s law
Malus law
Meyer’s eq
Brewster’s law
Brewster’s angle
Delong Petit law
Critical isotherm
Liquid vapor region

 Posts: 27
 Joined: Mon Jul 29, 2013 4:33 pm
Re: 19th NOV 2013 test  study group
Tomorrow exam.Best of luck for everyone.
There's a song(with no melody although) on you tube based on PGRERobert Lee,Steve Sigda(Oct8,2010).Now our time has come.
Song based on Wonder wall of OASIS.
There's a song(with no melody although) on you tube based on PGRERobert Lee,Steve Sigda(Oct8,2010).Now our time has come.
Song based on Wonder wall of OASIS.
Re: 19th NOV 2013 test  study group
yes gfood luck to everyone
meanwhile can someone explain what is happening in the following sums 
2001  84
199641 and
198684
http://grephysics.net/ans/8677/84
meanwhile can someone explain what is happening in the following sums 
2001  84
199641 and
198684
http://grephysics.net/ans/8677/84