Final answer:
When light travels from a rarer to a denser medium, it experiences a decrease in both velocity and wavelength.
Step-by-step explanation:
As light travels from a rarer to a denser medium, its velocity decreases and the wavelength also decreases. This is because light will always travel slower in a denser medium than in a rarer one, like air. For example, when light travels in water it moves at three-fourths the value it would in a vacuum (the speed of light in a vacuum is denoted by 'c'). When light passes into a denser medium like glass or water from air, its speed decreases, and the wavelength also becomes shorter due to the relationship between speed, wavelength, and frequency (which remains constant), as described by the equation speed = wavelength × frequency. Therefore, the correct answers are:
- B. Decreased velocity
- C. Decreased wavelength