The speed of light in a medium is calculated using the formula v = c/n, where v is the speed of light in the medium, c is the speed of light in vacuum, and n is the refractive index of the medium. For glass with a refractive index of 1.50, the speed of light in glass is (3 × 10⁸)/1.5 = 2 × 10⁸ m/s.

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## Introduction to Light Speed in Different Media

*Fundamental Properties of Light*: The speed of light varies when it travels through different media. In a vacuum, it travels at its maximum speed, but this speed decreases when light passes through any material medium due to interactions with the medium’s particles.

### Speed of Light in Vacuum

*Maximum Velocity of Light*: In a vacuum, light travels at a speed of approximately 3 × 10⁸ meters per second (m/s). This speed is considered a fundamental constant of nature and is the fastest speed at which energy or information can travel.

#### Refractive Index of Glass

*Optical Density Indicator*: The refractive index of a medium is a measure of how much the speed of light is reduced inside the medium compared to its speed in a vacuum. For glass, the refractive index is given as 1.50, indicating that light travels slower in glass than in a vacuum.

##### Calculating Light Speed in Glass

*Applying the Formula*: The speed of light in a medium can be calculated using the formula v = c/n, where v is the speed of light in the medium, c is the speed of light in a vacuum, and n is the refractive index of the medium.

###### Result of the Calculation

*Determining the Speed in Glass*: Substituting the known values into the formula,

v = (3 × 10⁸)/1.5, we find that the speed of light in glass is approximately 3 × 10⁸ m/s.

*Implications in Optics*: This reduced speed of light in glass has significant implications in optics, affecting how light beams bend (refract) and how lenses and prisms in optical devices manipulate light. Understanding these principles is crucial in designing various optical instruments and technologies.

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