lesson 1. watch the slinky… slinky videos

General Wave PropertiesLesson 1

Watch the Slinky…Slinky videos

http://www.youtube.com/watch?v=VnfiZfyQ2ywhttp://www.youtube.com/watch?v=upcTmdqrEe

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What is a Wave?Transfer of energyIn the form of disturbance through some

medium*Without translocation of the medium

* Not all waves require a medium

Transverse Waveshttp://www.surendranath.org/Applets/Waves/

Twave01/Twave01Applet.html

Longitudinal Waveshttp://www.surendranath.org/Applets/Waves/

Lwave01/Lwave01Applet.html

Wave TerminologyDescriptions

Wave Terminology

Crest/Peak – high point of a transverse waveTrough – low point of a transverse wave

crest

trough

Wave Terminology

(In a longitudinal wave)Compression – region of high pressureRarefaction – region of low pressure

Wave Terminology

Phase – two points are said to be in phase if they are moving in the same direction and speed, with the same displacement from the rest position

p q p” q”p’ q’

Wave TerminologyWavefront – Imaginary line joining all points

in the same phase of vibration (e.g. all the crests)

Wave TerminologyQuantities

Wave Terminology

Amplitude – maximum displacement of a particle from its mean position (on either side)

SI Unit: m

A

A

AA

AA

Wave Terminology

Wavelength – distance between two successive particles which are oscillating in phase

SI Unit: m

Wave TerminologyFrequency (f): number of

vibrations/oscillations/cycles in 1 second.SI Unit: s-1 or Hz

Period (T): time taken for one complete vibration/oscillation/cycle.

SI Unit: s

T = 1/f

Wave EquationCalculating wave speed

Wave EquationWave speed/velocity (v): distance moved by

the wave in one secondSI Unit: ms-1

(Discuss) How to calculate v using the wave quantities covered earlier?

Wave EquationWith the wavelength and frequency of a wave, we know how many waves and how far the series of waves will cover per unit time. This is known as wave speed – distance traveled by a wave per unit time.

Recall speed =

So for waves, speed v = distance covered in 1 cycletime taken to cover 1 cycle

Recall f

so speed of waves v =

Speed equation for waves v = f (Unit : ms-1)

distance

time

wavelength

period

1

T

fT

1

T T

Test yourself…A fisherman notices that wave crests pass the bow of his anchored boat every 3.0s.He measures the distance between two successive crests to be 6.5m.How fast are the waves travelling?

EndComplete pages 1, 3, 7 of the Class Worksheet (Notes).