The light bends towards the normal line so that the angle of refraction is less than the angle of incidence. This amount of bending is also related to the change of speed of the light. Light travels slower in diamond than it does in glass and slower in glass then it does in water.

Snell’s Law and the Speed of Light The higher the index of refraction is, the slower the speed of light is. The indexes of refraction for diamond, air and glass are, respectively, 2.42, 1.00, and approximately 1.50, depending upon the composition of the glass. Light travels slowest in diamond.

Refractive index of water with respect to air is 1.33 and that of diamond is 2.42. (i) In which medium does the light move faster, water or diamond? Refractive index = speed of light in vacuum / speed of light in medium. Since the refractive index of diamond is more, hence the speed of light is lesser in diamond.

The speed of light in diamond is 1.24 x 108 m/s.

225,000 kilometers per second

Scientists have long known that the speed of light can be slowed slightly as it travels through materials such as water or glass. They have demonstrated that applying a mask to an optical beam to give photons a spatial structure can reduce their speed.

Light, no matter how high-or-low in energy, always moves at the speed of light, so long as it’s traveling through the vacuum of empty space. And to the best of our knowledge and measurements, the speed of light has the same value of 299,792,458 m/s at all times and all locations in the Universe.

Red light

violet light

In air, glass, water and many other transparent materials, red light travels faster than blue light.

Since in general the index of refraction is bigger for shorter wavelengths, blue light bends more than red light.