Multipath Microwave EM: Max & Min Intensity Regions

[aidandv]

Homework Statement

I am struggling to understand why the fact the plate knocks the waves a further 180 degrees out of phase that you have to multiply your anseer for wavelength after using pythagoras by 2?

Relevant Equations

a^2+b^2=c^2

 

[hutchphd]

The 180 deg phase shift upon reflection from a conductor comes from the electrodynamics and not simply the wave interference.
As for the factor of 2: what is "your answer" that you need to multiply by two? .

 

[aidandv]

The 180 deg phase shift upon reflection from a conductor comes from the electrodynamics and not simply the wave interference.
As for the factor of 2: what is "your answer" that you need to multiply by two? .

The answer is 2.8 not 1.4, how does the wave getting knocked out of phase by 180 degrees mean my calculation for wavelength is off by a factor of 2?

 

[hutchphd]

You have calculated only half of the path ! The 180 phase shift upon reflection is there for all paths and so doesn't matter for path differences. (Your mistake is a little worse than I suspected).

 

[aidandv]

im sorry but i do not understand what you mean. Adjacent maxima are 1 full wavelength apart and that is what i have calculated

 

[hutchphd]

One wavelength along the total path. What is tha total path length from source T to observor O ? You calculated half of it.

 

[aidandv]

i thought because it converges back to a singular point it doesnt matter, i see my mistake now thank you. How would you answer the non-calculation part of the question?

 

[hutchphd]

Explicitly what? How would you answer?....I will critique.

 

[hutchphd]

converges back to a singular point it doesnt matter

The 180 reflection shift is a shift of Outgoing phase relative to Incoming phase and does not "reset" anything. It makes the wave be zero on that surface (as required for a conductor)

 

[aidandv]

When 2 or more microwaves come togetehr at the receiver they superpose and the resultant wave displacement is the sum of the individual waves displacements. Maxima exist when the waves are even pi radians out of phase and therefore the max displacements of the incident waves add up to create a larger maximum displacement for the result waves, similarly minima exist when the waves are odd pi radians out of phase, the displacements cancel out and result in no displacement at that point in the resultant wave. Anything I’m missing?

 

[kuruman]

This is the same question as your previous thread and you said that you know how to calculate the wavelength from each individual value of $y$.

Yes I understand how you only require one as long as you know the order. Thanks for helpjng

Do that calculation and you will see where the factor of 2 comes form. Doing so will answer what you call the "non calculation part of the question." If you cannot do the calculation, post whatever you can do here (right side up please or use preferably LaTeX) and we will help you finish it.

Your statements in post #10 are generalities that are not specific to this problem. Finding the wavelength from 4 separate calculations will clinch the argument. You should also explain why the first occurrence of an extremum at y = 8.4 cm is a maximum and not a minimum.