Question

the light from a helium neon laser has a wavelength of 632 nanometers in air. the same light has a wavelength of 479.2 in glass. the frequency of the light is the same in air and glass. find the speed of the laser light in glass.

Answer 1

speed (m/s) = wavelength (m) * frequency (1/s)

v = λf

so, for a given frequency, the velocity is directly proportional to the wavelength.

Get v in air, and then you can figure v in glass.

Answer 2

speed = wavelength * frequency

so, the speeds are in the same ratio as the wavelengths

sglass = sair (wglass / wair)