Light Having a Wavelength in Vacuum Of $600 \mathrm {~nm}$ Enters a Liquid of Refractive Index

Multiple Choice

Light having a wavelength in vacuum of $600 \mathrm {~nm}$ enters a liquid of refractive index $2.0$ . In this liquid, what is the wavelength of the light? $\left( c = 3.0 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right)$

A) 600 nm
B) 300 nm
C) 200 nm
D) 150 nm
E) 1200 nm