# Is there a wave having frequency below ELF?

1. May 31, 2014

### vishnumanu

speed of light = wavelength X Freq. Suppose Freq of the wave is 1 Hz, then isn't ist possible that the wavelength is equal to the speed of light? Is there anything like that?

2. May 31, 2014

### Matterwave

If the frequency is 1 Hz, the wavelength is ~300,000km. A wavelength is a length, and not a speed. It doesn't make sense to say "wavelength equals speed of light" because they don't measure the same thing. It's like saying "I weigh 40 miles per hour", or "I can run at a speed of 40lbs". You can't compare things that don't have the same units.

You can certainly have a 300,000km long electromagnetic wave, there's no rules in physics forbidding this. It would be an ultra-low-frequency wave for sure, but nothing theoretically prevents this.

3. May 31, 2014

### vishnumanu

yes i actually meant was that such kind of a wave will have a 300000 km long cycle. sorry for the wrong way of expressing it. English is not my main lang.
One more question... :)
Is it also possible to have waves having frequency less than 1 hz?

4. May 31, 2014

### Drakkith

Staff Emeritus
Yes, EM waves can have a frequency less than 1 hz. They are just very difficult to create.

5. May 31, 2014

### Staff: Mentor

They're easy to create; it's detection that's difficult. Hold a charged object (static electricity from stroking the cat is fine) in your hand, and then move your hand back and forth at whatever frequency you want. You're generating EM radiation at that frequency.

6. May 31, 2014

### vanhees71

The point is that you won't realize that you create em. waves, because you measure the field at distances from the source which is (very) small compared to the wavelength of your wave, and there the quasistatic approximation is fine, i.e., you'll measure something like a time-dependent field which behaves as an electrostatic and magnetostatic field from the ("slowly") moving source rather than something which is approximately like a (plane) wave, which you only get when going to distances from the source large compared to the wavelength.

7. May 31, 2014

### Drakkith

Staff Emeritus
I was thinking of trying to create them with an antenna, where the higher the frequency the easier it is to create.