Intensity of waves

[Niha afzal]

And this time I have no idea even how to start the problem. I just know one thing I DIRECTLY PROPORTIONAL TO R^2 and the other formulae relating radius is given in the question..... now how to I relate both of them

[studiot]

What do the terms 'intensity' and 'amplitude' mean and what is the relationship between them ?

[Niha afzal]

Intensity is the brightness of the wave ... and the eq INTENSITY DIRECTLY PROPORTIONAL TO AMPLITUDE^2 relates them

And amplitude is the maximum displacement of the wave

Edited March 27, 2016 by Niha afzal

[studiot]

Yes, but brightness is still a vagueish term.

 

The intensity is a measure of the energy of the wave (per uint area or volume) and, as you say it is proportional to the square of the amplitude.

 

So [math]I \propto {A^2}[/math]

 

[math]I = {k_1}{A^2}[/math]

 

and

 

[math]I \propto \frac{1}{{{r^2}}}[/math]

or

 

[math]I = \frac{{{k_2}}}{{{r^2}}}[/math]

Can you now combine these two equations to find the answer?

 

 

[Niha afzal]

Yes .... the squares get cancelled out leaving me with B