Frequency Explained for Toddlers: Visible/Audible Range?

[Suryadavinci]

I am just a toddler. Please explain me about frequency. What shapes do waves have? Do all waves travel like the waves produced, when a stone is dropped on water? And when the frequency of a signal is varied and if the new frequency is in the visible region or audible range, Can i see or hear it?

 

[Drakkith]

I am just a toddler. Please explain me about frequency. What shapes do waves have? Do all waves travel like the waves produced, when a stone is dropped on water?

Take a look at these links.
http://en.wikipedia.org/wiki/Frequency
http://en.wikipedia.org/wiki/Wave

And when the frequency of a signal is varied and if the new frequency is in the visible region or audible range, Can i see or hear it?

I guess it depends on how you are modifying the wave. I've never heard of anything directly modifying waves before. Usually something measures the incoming wave and the emits a new one at a new frequency if need be.