Doubt in physics

how to find intensity at the given points in such case.

can anybody please help me, my question is how to find intensity at A,B,C,D,
what i know that is as constructive interference takes place at all points therefore intensity must be same at all places but it is not.

question is from narayan gta10 p2

plz somebody help here

The resultant amplitude at each point can be found using phasor method.

First find phase difference at each point on X axis. You should get ∆phase = (2pi/lambda)(|x| - |x-20|)

Now draw two phasors representing the different waves emanating from each source. One of magnitude 2A, and the other of magnitude 4A, and the angle between them equal to the phase difference as obtained earlier.

The magnitude of the resultant phasor should give you the net amplitude at any point along X axis. Now find amplitud

1 Like

i dont understand the phase difference . how you get that @Ishaan_Shrivastava


oh that was a misprint. check it again now

i edited it now

1 Like

okay so for every case possible the phase difference will be a multiple of pi and thus only destrutive oor constructive interference will take place but in answer the intensities at every point was different

maybe i misunderstood the question. @Rudra_d @KrishSharma help?


this was a match the column type and these were the options

1 Like

II - S


See phase difference is used to find constructive or destructive but intensity does not only depends on this.

1 Like


And in 16 ques just interchange


Ohhhh yeaaaaa I forgot that other factor

can you plz elaborate

He means that intensity of a beam of light depends on the distance from the source too. So you have to write your phasor diagram accordingly

I \propto A^2/r^2


i probably dont know this.

thankyou ill try now.

1 Like