# NTNUJAVA: Virtual Physics Laboratory: Enjoy the fun of Physics

• request for applet /board:26-100- by:peacenloveat 2009/11/18 06:18hi
thank you so much for your amazing work here

you will have to excuse me as i don't posses a great knowledge of physics

i,m wondering if you could build us an applet in which one could enter a frequency
and it would show the major harmonics

eg Tesla and royal rife used 11.78 million Hz for treating cancer
so if i enter 11.78 into an applet it would give me the lower harmonics say down to under 10,000Hz and also a picture of the wave form as in sine wave and square wave etc

See 8 replies click

1. Re: request for applet /board:26-100- by:hwangat 2009/11/18 08:28You need to indicate that what is the waveform of your signal.
If the signal is a sine wave, then the frequency f of the sine wave is the lowest harmonic,
the other harmonic might be 2f,3f,...

If you are talking about the possible resonance with a system, then it will depend on what kind of system you are talking about. Each system has it's own characteristic frequency pattern.

2. Re: request for applet /board:26-100- by:peacenloveat 2009/11/19 07:47hi thank you for answering :)

the wave used is a square wave

there is this we use often http://www.csgnetwork.com/harmonicscalc.html

but it lacks the visual that your so clever at producing

it would be great to be able to choose a frequency and see its harmonics in values and its wave form kinda like you have produced here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1073.0
but where you have cos and sine it shows the harmonics and the wave form as is

i hope i,m making sence ;)

3. Re: request for applet /board:26-100- by:hwangat 2009/11/19 13:22The square is a superposition from infinite sine wave.
The Fourier series is $f(t)=\frac{4}{\pi} \sum_{n=1,3,5,...}^\infty \frac{1}{n}\sin(\frac{n\pi t}{T}).$
where L is the full length of the square wave.
You can check out http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=17.msg114#msg114 to find it's 1-15th components.

You can use the above equation to find out the relative intensity (1/n) of each component (harmonic).

4. Re: request for applet /board:26-100- by:peacenloveat 2009/11/20 04:58hi
thank you,,, :(
its a very comlex applet for sick people to try to use
i could not get the base frequency tone to change
and the results ment nothing

5. Re: request for applet /board:26-100- by:hwangat 2009/11/20 10:35You need to HIT ENTER after you change the number in the text box.
And you will be able to hear it when you click play.

You can also find all the value for those components, from the table just below the simulation.
Click button label as "get" to get values for all the components. You can change the value in the table and click "set" to change it in the simulation.
[code]its a very comlex applet for sick people to try to use[/code]
Sorry! If you can provide me suggestion: how to make it better, I will try to improve it.

6. Re: request for applet /board:26-100- by:peacenloveat 2009/11/26 05:04hi THANKS :)

COULD YOU DO AN Applet that shows two waves (frequencies) the same
and allows people to adjust and hear those frequencies from say 100 to 11,700hz

then allows them to phase shift by 90 or 180 and plays the result

7. Re: request for applet /board:26-100- by:hwangat 2009/11/26 16:58For two waves with the same frequency $\omega$ and amplitude, but only different by phase shift $\psi$
The result is $f=A \sin\omega t +A (\sin\omega t+\psi)= A \sin\omega t +A \sin\omega t \cos\psi+A\cos\omega t \sin\psi$
so $f= A(1+\cos\psi) \sin\omega t + A \sin\psi \cos\omega t=A\sqrt{(1+\cos\psi)^2+\sin\psi^2} \sin(\omega+\delta)=A\sqrt{2(1+\cos\psi)} \sin(\omega+\delta)$
where $\tan\delta=\frac{\sin\psi}{1+\cos\psi}$
So the result is a wave with the same frequency but different amplitude.
For special case, where $\psi=\pi$, the wave will cancel with each other, otherwise, you will not hear any different in sound frequence except sound level difference.

You can use EJS version of Fourier Synthesis (You can hear the sound,too!) to hear sound at different frequence.

Please check out Superposition of two waves to view the sum of two waves (with phase difference)

8. Re: request for applet /board:26-100- by:peacenloveat 2009/12/31 07:02HI
THANK YOU