The wavelength of light changes when it transitions between different media. The wavelength in the second medium (\( \lambda_2 \)) is related to the wavelength in the first medium (\( \lambda_1 \)) by the equation:
\[
\lambda_2 = \lambda_1 \frac{v_2}{v_1} = \lambda_1 \frac{n_1}{n_2}
\]
Here, \( \lambda_1 \) denotes the wavelength in the initial medium (water), and \( \lambda_2 \) is the wavelength in the subsequent medium (air).
Provided values:
- \( \lambda_1 = 600 \) nm
- \( n_1 = \frac{4}{3} \) (water)
- \( n_2 = 1 \) (air)
Calculation:
\[
\lambda_2 = 600 \times \frac{3}{4} = 450 \text{ nm}
\]
Therefore, the result is:
\[
\text{(B) } 450 \text{ nm}
\]