Nilo measures light's speed inside a clear plastic: 2.0 × 10⁸ m/s. He wants the plastic's index of refraction.
This lesson is the forward calculation: from the speed in the medium to n.
The givens are two speeds: c = 3.00 × 10⁸ m/s in a vacuum, and the measured v = 2.0 × 10⁸ m/s in the plastic.
The equation is the one OPT-028 defined: n = c/v.
Divide: 3.00 ÷ 2.0 = 1.5, and the two 10⁸ factors cancel. The plastic's index of refraction is 1.5.
The 10⁸ factors always cancel in this division, because both speeds carry the same power of ten. The whole calculation lives in the leading digits.
And n comes out without a unit: m/s divided by m/s leaves a pure ratio.
Light travels at 2.0 × 10⁸ m/s in a clear plastic. Calculate the plastic's index of refraction.
Write down the values:
c = 3.00 × 10⁸ m/s, v = 2.0 × 10⁸ m/s, n = ?
Write down the equation:
n = c/v
Substitute in the values, and calculate:
3.00 ÷ 2.0 = 1.5, and the 10⁸ factors cancel, so n = 1.5.
The plastic's index of refraction is 1.5.
Light travels at 2.04 × 10⁸ m/s in glycerin. Calculate glycerin's index of refraction, to two decimal places.
Write down the values:
c = 3.00 × 10⁸ m/s, v = 2.04 × 10⁸ m/s, n = ?
Write down the equation:
n = c/v
Substitute in the values, and calculate:
3.00 ÷ 2.04 = 1.47, and the 10⁸ factors cancel, so n = 1.47.
Glycerin's index of refraction is 1.47.
Light travels at 1.25 × 10⁸ m/s inside a gemstone. Calculate the gemstone's index of refraction, to two decimal places.
Light travels at 1.95 × 10⁸ m/s inside a salt crystal. Calculate the crystal's index of refraction, to two decimal places. Answers within 0.03 are accepted.
Oona says: 'Light always travels more slowly in a medium than in a vacuum, so a medium's index of refraction always comes out greater than 1.' Is Oona correct?
Light travels at 1.85 × 10⁸ m/s inside a dense glass. Calculate the glass's index of refraction, to two decimal places. Answers within 0.03 are accepted.
Light travels at 2.01 × 10⁸ m/s through a sample of honey. Calculate the honey's index of refraction, to two decimal places. Answers within 0.03 are accepted.
Light travels at 2.9 × 10⁸ m/s in warm air and at 1.9 × 10⁸ m/s in a glass paperweight. Which has the larger index of refraction?