Light | Show Me The Physics

Narrated Lesson

showmethephysics.com

Resonance Review

UC Irvine

School blocks YouTube?
Download the file below.

Bubbles
1st, 2nd, 3rd Harmonic
(B. Barrett)

A. Speed

1. 3 x 10⁸ m/s = c (in vacuum)

(fastest speed in universe)

In air v ≈ 3 x 10⁸ m/s

Did you know that
light can travel
about 7.5 times around the world
in 1 second!

v = fλ

c = fλ

3 x 10⁸ m/s = fλ

Divide both sides by λ

f = c/λ

Frequency, Wavelength

Relationship?

Inverse

Ex) What is the wavelength of light with a frequency of 7.69 x 10¹⁴Hz in a vacuum?

c = fλ

3 x 10⁸ m/s = 7.69 x 10¹⁴ Hz λ

λ = 4 x 10^-7 m

2. Speed of light depends on the medium

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. What is the speed of light in a vacuum?

2. What is the wavelength of light with a frequency of 6.0 × 10¹⁴ Hz in a vacuum?

3. For light in a vacuum, how are frequency and wavelength related?

4. The speed of light depends on

5. Sunlight reaches Earth through the vacuum of space, but sound from the Sun cannot. Why?