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**EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 3-1 Properties of Waves**

Edexcel IGCSE Physics pages 91 to 98 Content applying to Triple Science only is shown in red type on the next slide and is indicated on subsequent slides by ‘TRIPLE ONLY’ June 17th 2012

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**Edexcel Specification**

Section 3: Waves b) Properties of Waves understand the difference between longitudinal and transverse waves and describe experiments to show longitudinal and transverse waves in, for example, ropes, springs and water define amplitude, frequency, wavelength and period of a wave understand that waves transfer energy and information without transferring matter know and use the relationship: wave speed = frequency × wavelength v = f × λ use the relationship: frequency = 1 / time period f = 1 / T use the above relationships in different contexts including sound waves and electromagnetic waves understand that waves can be diffracted when they pass an edge understand that waves can be diffracted through gaps, and that the extent of diffraction depends on the wavelength and the physical dimension of the gap. Red type: Triple Science Only

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Waves A wave is a means of transferring energy and information from one point to another without there being any transfer of matter between the two points. 3

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Transverse Waves Transverse waves are waves where the direction of vibrations is at 90° to the direction in which the wave travels. example: water waves wave direction vibrations TRANSVERSE WAVE

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Longitudinal Waves wave direction vibrations LONGITUDINAL WAVE Longitudinal waves are waves where the vibrations of the particles are along the direction in which the wave travels. example: sound waves longitudinal wave in slinky

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**Describing Waves 1. Amplitude (A)**

Amplitude is the maximum movement of the particles that make up a wave from their rest position. amplitude rest position amplitude The amplitude is the height of a crest OR the depth of a trough 6

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2. Wavelength (λ) Wavelength is the distance between one wave peak and the next wave peak along the path of a wave. Wavelength is measured in metres. wavelength wavelength Wavelength is also the distance between the bottom of one trough to the next. 7

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3. Frequency (f ) Frequency is the number of wave peaks that pass a point in one second. Frequency is measured in hertz (Hz) 1 Hz = 1 peak per second 2 Hz = 2 peaks per second and so on…. 1 kilohertz (1kHz) = Hz 1 megahertz (1MHz) = Hz 1 gigahertz (1GHz) = Hz 1 terahertz (1THz) = Hz 8

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**T = 1 / f f = 1 / T 4. Time period (T )**

Time period is the time taken for a source to produce one wave. time period = frequency and: frequency = time period T = 1 / f f = 1 / T 9

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Question 1 Calculate the frequency of a wave of time period 8.0 seconds. f = 1 / T = 1 / 8 frequency = hertz 10

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**Question 2 Calculate the time period of a wave of frequency 50Hz.**

T = 1 / f = 1 / 50 time period = second 11

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**speed = frequency x wavelength**

The wave equation speed = frequency x wavelength v = f x λ speed in metres per second (m/s) wavelength in metres (m) frequency in hertz (Hz) also: f = v ÷ λ and: λ = v ÷ f v f λ 12

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Question 1 Calculate the speed of a water wave of wavelength 3m and frequency 6Hz. v = f x λ = 6Hz x 3m speed = 18 m/s 13

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Question 2 Calculate the frequency of a wave in water of wavelength 2.0m if its speed is 16m/s. v = f x λ becomes: f = v ÷ λ = 16 m/s ÷ 2m frequency = 8 Hz 14

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Question 3 Calculate the wavelength of a sound wave in water of frequency 300Hz if its speed is 1500m/s. v = f x λ becomes: λ = v ÷ f = 1500 m/s ÷ 300 Hz wavelength = 5 metres 15

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Question 4 Calculate the speed of a wave that has a wavelength of 30m and time period 0.04s. f = 1 / T = 1 / 0.04s f = 25 hertz v = f x λ = 25Hz x 30m speed = 750 m/s 16

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**Complete: Answers v f λ 60 m/s 165 Hz 200 000 Hz 3 m 15 Hz 4 m 330 m/s**

km/s 100 MHz 60 m/s 165 Hz Hz 3 m 17

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TRIPLE ONLY Diffraction Diffraction occurs when waves spread out after passing through a gap or round an obstacle. Sea wave diffraction

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TRIPLE ONLY Diffraction becomes more significant when the size of the gap or obstacle is reduced compared with the wavelength of the wave.

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**Choose appropriate words to fill in the gaps below:**

A wave transfers _______ without the movement of _______ from one place to another. In a __________ wave the particle ____________ are perpendicular to the direction of wave travel. Frequency is equal to the number of waves produced by a source in one _________. Time period is equal to the ___________ of the frequency. The speed of a wave in m/s is equal to its __________ in metres multiplied by its __________ in hertz. energy matter transverse vibrations second reciprocal wavelength frequency WORD SELECTION: frequency transverse reciprocal energy second vibrations wavelength matter

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Online Simulations Simple demonstration of longitudinal & transverse waves - Freezeway.com Wave lab - shows simple transverse & longitudinal waves with reflection causing a stationary wave - by eChalk Wave Effects - PhET - Make waves with a dripping faucet, audio speaker, or laser! Add a second source or a pair of slits to create an interference pattern. Also shows diffraction. Virtual Ripple Tank - falstad Fifty-Fifty Game on Wave Types - by KT - Microsoft WORD Simple transverse wave - netfirms Simple longitudinal wave - netfirms Simple wave comparision - amplitude, wavelength - 7stones Wave on a String - PhET - Watch a string vibrate in slow motion. Wiggle the end of the string and make waves, or adjust the frequency and amplitude of an oscillator. Adjust the damping and tension. The end can be fixed, loose, or open. Vend diagram quiz comparing light and sound waves - eChalk BBC AQA GCSE Bitesize Revision: What are waves Amplitude, wavelength and frequency Wave speed

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**Properties of Waves Notes questions from pages 91 to 98**

TRIPLE ONLY Properties of Waves Notes questions from pages 91 to 98 (a) What is a wave? (b) Explain the difference between a transverse and longitudinal wave (see pages 91 and 92) Define what is meant by (a) amplitude; (b) wavelength; (c) frequency and (d) time period. (see pages 92 and 93) (a) State the wave equation. (b) Calculate the wavelength of a radio wave of frequency 10MHz, speed km/s.(see pages 93 and 94) (a) What is wave diffraction? (b) Draw diagrams showing how diffraction is affected by the wavelength of a wave. (see page 97) Answer the questions on page 98. Verify that you can do all of the items listed in the end of chapter checklist on page 98.

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**Properties of Waves Notes questions from pages 91 to 98**

DOUBLE ONLY Properties of Waves Notes questions from pages 91 to 98 (a) What is a wave? (b) Explain the difference between a transverse and longitudinal wave (see pages 91 and 92) Define what is meant by (a) amplitude; (b) wavelength; (c) frequency and (d) time period. (see pages 92 and 93) (a) State the wave equation. (b) Calculate the wavelength of a radio wave of frequency 10MHz, speed km/s. (see pages 93 and 94) Answer questions 1, 3 and 4 on page 98

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