P 7 Waves This lesson What is a

P 7 Waves

This lesson • What is a wave? • Longitudinal and transverse waves • Amplitude, wavelength, frequency and period of a wave • The relationship between frequency and period • The wave equation

What is a wave? You. Tube - Water bubble in Space (zero gravity) http: //www. youtube. com/watch? v=x. Unadiy. PTks http: //www. youtube. com/watch? v=B 01 vktb 2 bj 4

Waves can transfer energy and information without a net motion of the material through which they travel. They involve vibrations (oscillations) of some sort.

Waves can transfer energy and information without a net motion of the material through which they travel. They involve vibrations (oscillations) of some sort. Can you do something very boring and traditional……… Can you copy this please?

Transverse waves The oscillations are perpendicular to the direction of energy transfer. peak Direction of energy transfer oscillation trough

Transverse waves • Water ripples • Light • On a rope/slinky • Earthquake

Longitudinal waves The oscillations are parallel to the direction of energy transfer. Direction of energy transfer compression oscillation rarefraction

Longitudianl waves compression rarefraction

Longitudinal waves • Sound • Slinky • Earthquake

Wave measurements

Amplitude - A The maximum displacement from the mean (average) position. amplitude

Frequency - f The number of oscillations/waves in one second. Measured in Hertz. 50 Hz = 50 vibrations/waves in one second.

Wavelength - λ The length of one complete wavelength

Wave speed - v The speed at which energy is transferred along the wave 330 m. s-1

The Wave Equation v = fλ v = speed (m/s) λ = wavelength (m) f = frequency (Hz) v f x λ

Some example wave equation questions 1) A water wave has a frequency of 2 Hz and a wavelength of 0. 3 m. How fast is it moving? 0. 6 m/s 2) A water wave travels through a pond with a speed of 1 m/s and a frequency of 5 Hz. What is the wavelength of the waves? 0. 2 m 3) The speed of sound is 330 m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 0. 5 m 4) Purple light has a wavelength of around 6 x 10 -7 m and a frequency of 5 x 1014 Hz. What is the speed of purple light? 3 x 108 m/s

Wave equation questions v f x λ

Let’s try some questions! Page 125 (all the questions) and page 136 questions 1 and 4.