# Lasers & Frequency: Exploring Light Harmonics

• Niles
In summary, when discussing sound and lasers, we use the terms fundamental frequency, first harmonic, second harmonic, etc. for both. However, while sound can produce standing waves, this is not possible with light. Most lasers operate at just one frequency, the fundamental, but some, such as green laser pointers, use the second harmonic.

## Homework Statement

Hi all.

When talking about sound, we tak about the fundamental frequency, the first harmonic, second, third etc.

Does this also work for lasers, i.e. for light? So if I have a laser at 500 nm, then the third harmonic is 3 times the frequency that corresponds to 500 nm?

Best regards,
Niles.

Good question, and I'm not totally sure.

The one thing I would say is that the conditions in order to produce a standing wave would never ever happen with light, perhaps theoretically if you could somehow have a fixed beam of light and control it with a perfect mirror, I'm not sure but i'll go with ; practically - no! =P

Niles said:

## Homework Statement

Hi all.

When talking about sound, we tak about the fundamental frequency, the first harmonic, second, third etc.

Does this also work for lasers, i.e. for light? So if I have a laser at 500 nm, then the third harmonic is 3 times the frequency that corresponds to 500 nm?

Best regards,
Niles.

Yes, that is true. Note however that most lasers operate at just one frequency, the fundamental, to a very good approximation. An exception to this is a typical green laser pointer; the green light is the 2nd harmonic of the fundamental, near-infrared frequency.

Thanks for that.