Which statement about the symbol c is correct?
Maud looks up two measured speeds. In a vacuum, light travels at 3.00 × 10⁸ m/s. In water, it travels at 2.26 × 10⁸ m/s.
Optically denser and less dense compare two media in words. This lesson turns the comparison into one number per medium.
Divide the two speeds: 3.00 × 10⁸ m/s ÷ 2.26 × 10⁸ m/s = 1.33. Light is 1.33 times slower in water than in a vacuum.
That ratio is the medium's own number. It does not depend on the beam, the angle, or the brightness: only on the medium.
n is a speed divided by a speed, so n carries no unit. It is a pure ratio.
Water's index of 1.33 means light travels at c/1.33 in water: divide the vacuum speed by 1.33 and you have the water speed.
A larger n marks a slower medium. So a larger n also marks the optically denser medium: n puts a number on the comparison OPT-025 made in words.
Every medium slows light at least a little, so every medium's n is greater than 1. A vacuum itself has n = 1 exactly.
Light travels at 2.26 × 10⁸ m/s in water. Calculate water's index of refraction.
Write down the values:
c = 3.00 × 10⁸ m/s, v = 2.26 × 10⁸ m/s, n = ?
Write down the equation:
n = c/v
Substitute in the values, and calculate:
3.00 ÷ 2.26 = 1.33, and the two 10⁸ factors cancel, so n = 1.33. No unit: n is a ratio.
Water's index of refraction is 1.33.
Glycerin's index of refraction is 1.47. Without calculating, say what the 1.47 tells you about light in glycerin.
n compares the vacuum speed to the medium speed.
An index of 1.47 means light travels 1.47 times slower in glycerin than in a vacuum.
Glycerin's 1.47 is greater than water's 1.33, so glycerin slows light more than water does.
Light in glycerin travels at c/1.47, and glycerin is optically denser than water.
Light passes through three media: ice (n = 1.31), window glass (n = 1.52), and cubic zirconia (n = 2.16). In which medium does light travel slowest?
Water's index of refraction is 1.33. Which two speeds does the 1.33 compare?
Petrine says: 'A medium with an index of refraction of 2 slows light to half its vacuum speed.' Is Petrine correct?
Diamond's index of refraction is 2.42. Calculate the speed of light in diamond, in m/s, to three significant figures.
Four media are listed with their indices of refraction: ice (1.31), ethanol (1.36), window glass (1.52), sapphire (1.77). In which medium does light travel fastest?
Glycerin's index of refraction is 1.47. Which statement follows?