A laser beam has a wavelength of $500\text{nm}$ in vacuum. It enters a glass slab with refractive index $1.5$. Find its wavelength inside the glass.

Step-by-step solution

1. The wavelength inside a medium is related to the vacuum wavelength by ${\lambda }_{\text{medium}}=\frac{{\lambda }_{\text{vacuum}}}{n}$.
2. Substitute $n=1.5$ and ${\lambda }_{\text{vacuum}}=500\text{nm}$: ${\lambda }_{\text{glass}}=\frac{500}{1.5}\text{nm}.$
3. Compute the division: $500/1.5=333.33\text{nm}$ (to two decimal places).

Concept tested: Wavelength change in different media

Published 7 October 2026 · How this solution was prepared and checked