Answer:
When red light enters the lens its wavelength decreases but its frequency remains the same.
Explanation:
Lens is made of glass which is a denser medium when compared with air. Thus light will undergo refraction and bend toward the normal. On entering a denser medium from rarer medium the speed of light decreases.
Speed, frequency and wavelength of an electromagnetic wave are related according to the equation.
v=ϑλ
Where is v is the frequency, λ is the wavelength and v is the speed of the em wave.
On entering the lens the wavelength of the red light as well as speed decreases but the frequency remains the same.
