Answer:
a). [tex]2.25 \times 10^{8}[/tex] m/s
b).  1.23 m/s                Â
Explanation:
Given :
Index of refraction for water, [tex]n_{w}[/tex] = 1.33
Index of refraction of diamond, [tex]n_{d}[/tex] = 2.42
We know that,
Refractive index of any material is given by,
[tex]n = \frac{c}{v}[/tex]
where c = sped of light in air
      v = speed of light in any medium
a). Speed of light in water
  [tex]v = \frac{c}{n_{w}}[/tex]
  [tex]v = \frac{3\times 10^{8}}{1.33}[/tex]
  [tex]v = 2.25\times 10^{8}[/tex] m/s
b). Speed of light in diamond
  [tex]v =\frac{c}{n_{d}}[/tex]
  [tex]v =\frac{3\times 10^{8}}{2.42}[/tex]
   = 1.23 m/s