A laser beam with wavelength $550\text{ nm}$ in air strikes a glass slab of refractive index $1.50$. What is the wavelength of the light inside the glass?

Step-by-step solution

1. The speed of light in a medium is reduced by a factor of the refractive index: $v=c/n$.
2. Wavelength is related to speed and frequency by $\lambda =v/f$. Because the frequency $f$ is unchanged, the ratio of wavelengths in two media equals the ratio of speeds: ${\lambda }_{\text{glass}}={\lambda }_{\text{air}}/n$.
3. Insert the values: ${\lambda }_{\text{glass}}=550\text{ nm}/1.50$.
4. Compute: ${\lambda }_{\text{glass}}=366.67\text{ nm}$.

Concept tested: Wavelength reduction in denser medium

Published 10 October 2026 · How this solution was prepared and checked