Question

When a ray of light enters a glass slab from air then :

• A. Its wavelength decreases
• B. Its wavelength increases
• C. Its frequency increases
• D. Neither wavelength nor frequency changes

Answer 1

The correct option is A Its wavelength decreases

When a ray of light enters a glass slab from air then its speed decreases as it encounters a dense medium. Since to conserve energy (which is dependent solely on frequency), the frequency must remain constant, the wavelength of light changes. Wavelength is decreased by a factor called refractive index of the medium.