Green Light Giving Reddish Glow

Most recent answer: 02/22/2018

When I incident a green He-Ne laser through a prism, the color(basically the wavelength) changed to faint red(some other wavelength). Why is this happening?
- Prajwal Chettri (age 21)
Gangtok, Sikkim, India

I'm confused about the laser, since He-Ne lasers are red. Maybe it's a different type of laser?

I presume that the light mostly stayed green. A little will come out reddish orange due to Raman scattering in the glass. This is a process by which the light (made of photons) gives up a little of its energy in the form of sound waves (phonons). If a photon loses some energy to a phonon, then the frequency of the photon goes down, since E=hf, where E is energy, h is Planck's constant, and f is frequency.

Mike W.

(published on 02/22/2018)