As light undergoes refraction into a medium,

Step-by-step solution

When light travels from vacuum or air into an optically denser medium of refractive index n , its speed decreases according to the relation v = c n . The frequency f of light is a fundamental property of the source and remains unchanged during refraction across any boundary. Using the wave equation v = f , since the speed v decreases and the frequency f remains constant, the wavelength must decrease ( ' = n ). Therefore, its wavelength decreases while its frequency remains unchanged.