A question on wavelength

[dr.power]

Hi guys,

The formula for wavelength is LAMBDA = Speed x Period. So LAMBDA is the PERIOD times a coefficient.
But when it is shown by a sine drawing, it seems that wavelength is equal to the priod.
So am I right by saying that the speed coefficient in the LAMBDA formul is saying that the LAMBDA just is for outsides envirenment? Is it makes sense? For instance is the LAMBDA translatable for a sine generator circuit like a function generator? Or it is used for instance when the function generator is connected to a speaker so that show the distance the wave travel in the air?

Anyway I have a trouble to translate the wavelendth in real world for an speaker. I know what it is , but I am not sure how a100Hz sine wave at the ouput of a speaker having a wavelength more than 3 meter is detected by our ear. It is a really LONG wavelengh for our ears

 

[Nigel Goodwin]

Anyway I have a trouble to translate the wavelendth in real world for an speaker. I know what it is , but I am not sure how a100Hz sine wave at the ouput of a speaker having a wavelength more than 3 meter is detected by our ear. It is a really LONG wavelengh for our ears

I suggest you try your maths again - a 3 metre wavelength is VHF radio.

 

[jpanhalt]

Your formula is correct. The diagram technically is plotting intensity vs. DISTANCE on the X-axis. A plot of time on the X-axis will look the same, but then you would convert the time to distance to get wavelength using your formula.

Here's an example with real numbers. The velocity is not exact. Assume sound of 500 Hz with a velocity of 1000fps or its metric equivalent (where are you?).

The period is 1 sec /500 Hz = 2X10E-3 (2 millisecond). The wavelength would therefore be (.002 sec)x (1000 feet/sec) = 2 feet.

John

 

[dr.power]

I suggest you try your maths again - a 3 metre wavelength is VHF radio.

The Speed of the sound in air is almost 330m/s. So the wavelengh would be 330/100 =3.3m

 

[davenn]

The Speed of the sound in air is almost 330m/s. So the wavelengh would be 330/100 =3.3m

yes you are correct

Nigel is forgetting the difference between the speed of light and the speed of sound.
as a result the wavelength of a 100 MHz radio signal just happens to be really close to a 100Hz sound signal ie. ~ 3 metres

wavelength (Lambda) RF signal = 300,000(km/sec)(speed of light) / 100,000kHz (100MHz) = 3 metres
wavelength (Lambda) Audio Signal = 343 (m/s) speed of sound at sealevel and 20C temp) / 100Hz = 3.43 metres

when doing RF wavelength calc's which is what I'm into rather than sound, to make it easier we get rid of some of the 000's of each side of the equation and just
divide 300 by the frequency in MHz to get an answer in metres ie. 300 / 100 = 3m

cheers
Dave