How wavelength and velocity of light related?

Light of wavelength 5000 Å falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light ? For what angle of incidence is the reflected ray normal to the incident ray?

Define the wavelength of a sound wave. How is it related to the frequency and the wave spreed ?

What is the range of wavelength of visible light rays?

Predict how the velocity of light is changed when it travels from a material with higher refractive index to a material with lower refractive index.