Answer
(a) The speed of light in water is $2.26\times 10^8~m/s$
(b) The wavelength in water is $387~nm$
Work Step by Step
(a) We can find the speed of light in water:
$v = \frac{c}{n}$
$v = \frac{3.0\times 10^8~m/s}{1.33}$
$v = 2.26\times 10^8~m/s$
The speed of light in water is $2.26\times 10^8~m/s$
(b) We can find the wavelength $\lambda'$ in water:
$\lambda' = \frac{\lambda_0}{n}$
$\lambda' = \frac{515~nm}{1.33}$
$\lambda' = 387~nm$
The wavelength in water is $387~nm$.
