wavelength

[madame99]

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When a light wave passes from air into water, its frequency doesnt change but its speed does. Why doesnt the wavelength change as well? since v=fλ, I thought if velocity changes and frequency remains constant then wavelength would have to change.

 

[bluemonkey]

When a light wave passes from air into water, its frequency doesnt change but its speed does. Why doesnt the wavelength change as well? since v=fλ, I thought if velocity changes and frequency remains constant then wavelength would have to change.

You are correct. When light strikes a boundary of different indexes of refraction, the frequency is constant, the velocity changes, which means the wavelength must change as well.