Will mark as brainliest if
light refracts when its changes as it enters a new medium.
a. color
b. speed
c. source
d. frequency

Light refracts when its speed changes as it enters a new medium.

Explanation:

Bending of light wave while it entering a medium with different speed is called refraction of light. Light passing from a faster medium to the slower medium bends the light rays toward the normal to boundary between two media. The amount of the  bending of light depends on refractive index of the two media which is described by  the Snell's Law. The angle of incidence is not equal to  angle of refraction. Rainbow is caused but this refraction phenomena. Also Refraction is used in magnifying glasses, prism and lenses

the answer would be   dignified - apex