Step 1: Find the wavelength and speed of reflected light.
In the same medium through which the incident ray passed the ray will be reflected back. Therefore the wavelength, speed, and frequency of the reflected ray will be the same as that of the incident ray.
Hence, wavelength, $\lambda$ = 589 nm = 589 x 10^-9 m
Speed of light in air, c = 3 x 10⁸ m s^-1
Step 2: Find the frequency of reflected light.
\(\nu =\frac{c}{\lambda }=\frac{3\times10^{8}}{589\times10^{-9} }=5.09\times10^{14}~Hz\)

(b) 
Hint: The frequency of light does not depend on the property of the medium.
Step 1: Find the frequency of refracted light.
The frequency of light that is traveling never depends upon the property of the medium. Therefore, the frequency of the refracted ray in water will be equal to the frequency of the incident or reflected light in the air.
Refracted frequency = 5.09 x 10¹⁴ Hz.
Step 2: Find the speed of light.
\(v=\frac{c}{\mu }=\frac{3\times10^{8}}{1.33 }=2.26\times10^{8}~m/s\)
Step 3: Find the wavelength of light in water.
\(\lambda=\frac{v}{\nu }=\frac{2.26\times10^{8}}{5.09\times10^{14} }=444.007\times10^{-9}~m.=444.01~nm.\)

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