Expert: James J. Kovalcin - 11/1/2009

Question
Respected Sir I am Mukul Of grade 12
Why does the wavelength of light change but the frequency doesn't when it moves into a different medium?

Answer
When two mediums meet they form an interface. When a wave traveling in one medium encounters a second medium the vibrations in the first medium generate a corresponding vibration in the second medium which has the same frequency. The wavelength, however, is going to be affected by the speed with which the wave travels in the second medium. If the wavelength is longer in the second medium the wave speed will also be proportionally greater. It would be reasonable to look at the frequency as being the ratio of the wave speed to the wavelength in a particular medium that remains constant as the wave moves from one medium to another.