Question

Hello ...☺

Numerical question !!

Solve it with full steps

Answer 1

Final Answer :
Time Interval after which particles undergoes a phase change of π will be

2.5ms,7.5ms,12.5ms,.............


But, In options there is only 2.5ms,
So, (a) is the only answer.


However, if this Question was asked JEE

ADVANCED then they must have given

multiple correct options like 7.5ms ,12.5ms etc.

Then, these options are also to be marked.
::::::


Now , let us deal with the Question

Understanding :

1)
By Definition of
Minimum distance between two particles in same phase is Wavelength.
So,
lambda = 18 cm


2) Time Period of wave

= Wavelength / Speed of wave

3) Minimum Time Interval after which the given particles undergoes a phase change of π

is half of Time Period.

But, for just Time interval after phase change of π
= (2n+1)/2 T

= T/2 , 3T/2, 5T/2,......

For Calculation See Pic

Hope, you understand my answer.

If not tell me :

Answer 2

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