Answer
The wavelength of the laser beam in the liquid is 459 nm
Work Step by Step
We can find the speed in the liquid.
$v = \frac{d}{t}$
$v = \frac{0.30~m}{1.38\times 10^{-9}~s}$
$v = 2.174\times 10^8~m/s$
We can find the index of refraction of the liquid.
$v = \frac{c}{n}$
$n = \frac{c}{v}$
$n = \frac{3.0\times 10^8~m/s}{2.174\times 10^8~m/s}$
$n = 1.38$
We can find the wavelength in the liquid.
$n = \frac{\lambda_a}{\lambda_l}$
$\lambda_l = \frac{\lambda_a}{n}$
$\lambda_l = \frac{633~nm}{1.38}$
$\lambda_l = 459~nm$
The wavelength of the laser beam in the liquid is thus 459 nm.
