# Refractive index

Refractive index, often denoted by the symbol n, quantifies how much slower light moves through a given medium compared to its speed in a vacuum.

• Refractive index applies across the entire electromagnetic spectrum, spanning wavelengths from gamma-rays to radio waves.
• Every material through which light can travel has its own refractive index . It is calculated as the speed of light in a vacuum divided by the speed of light in a medium.
• For instance, water has a refractive index of approximately 1.333, signifying that light travels about 0.75 times slower through water compared to vacuum.
• During refraction, where light changes direction as it moves between different mediums, its wavelength alters due to the change in speed. However, the frequency, and thus the colour perceived by the human eye, remains constant.
• Importantly, the refractive index doesn’t impact the energy transported by light, only its speed and direction.
• When light undergoes refraction, its wavelength changes as its speed changes.
• When light undergoes refraction, its frequency remains the same.
• Neither refraction in general nor the refractive index of a particular medium affect the energy transported by light.
• The frequency of light and the amount of energy transported remain the same during refraction, so the perceived colour of refracted light by a human observer does not change.
###### References
• Refractive index, often denoted by the symbol n, quantifies how much slower light moves through a given medium compared to its speed in a vacuum.Refractive index applies across the entire electromagnetic spectrum, spanning wavelengths from gamma-rays to radio waves.
• Every material through which light can travel has its own refractive index . It is calculated as the speed of light in a vacuum divided by the speed of light in a medium.
• For instance, water has a refractive index of approximately 1.333, signifying that light travels about 0.75 times slower through water compared to vacuum.
• During refraction, where light changes direction as it moves between different mediums, its wavelength alters due to the change in speed. However, the frequency, and thus the colour perceived by the human eye, remains constant.
• Importantly, the refractive index doesn’t impact the energy transported by light, only its speed and direction.