`` NEWTON: Light Beats
Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page Visit Our Archives Ask A Question How To Ask A Question Question of the Week NEWTON Teachers Our Expert Scientists Volunteer at NEWTON! Referencing NEWTON Frequently Asked Questions About Ask A Scientist About NEWTON Education At Argonne Light Beats

Name: Kate
Status: other
Grade: 12+
Country: Australia
Date: Summer 2013

I am aware that two sound waves can overlap and result in a beat, and the frequency of the beat can be heard as a distinct third sound wave. Is the same possible for light? Can two light waves of different frequencies interfere and result in a third light wave being perceived?

Yes, although it's hard to achieve the conditions in which this can be observed. The only example I've ever seen is the scattering of x rays by a Mossbauer nucleus. The incident light excites nuclear resonances (when I say "excites a nuclear resonance", you should think "rings a bell inside the nucleus") that have very slightly different frequencies, and the radiation from those resonances interferes, producing a beat frequency that is the difference between the frequencies of the resonances.

However, in most cases of visible light interfering with visible light, the difference frequency will be lower than the frequency of visible light, so you will not actually perceive a third light wave.

Tim Mooney

Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

Educational Programs
Building 223
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: November 2011
Weclome To Newton

Argonne National Laboratory