Waves - General Wave Properties PDF

HOOK WHY ARE WE ABLE TO SEE during the day but not at night?  TOPIC 8:Waves LESSON 1– General Wave Properties Standard: MS-PS4-1: Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave. ...

HOOK WHY ARE WE ABLE TO SEE during the day but not at night?  TOPIC 8:Waves LESSON 1– General Wave Properties Standard: MS-PS4-1: Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave.  LEARNING OBJECTIVES Day 1: Define wave properties (wavelength, frequency, amplitude). Identify different types of waves.  Vocabulary Wavelength Frequency Amplitude Crest Trough What is a Wave? TURN and TALK Waves When a stone is dropped into a pond, ripples begin to spread out across the surface. Waves The tiny waves carry energy – but there is no actual flow of water across the pond. Waves Waves are just the up and down movement in water. Peak Trough  There are other sorts Waves of waves, such as: Waves are just the Sound up and down Radio movement in Light water. Peak Trough A wave is a disturbance that carries energy from place to place. A wave does NOT carry matter with it! It just moves the matter as it goes through it.  There are other sorts Types of Waves of waves, such as: Waves are just the Sound up and down Radio movement in Light water. Waves have features in common, and can be divided into three main types: 1. Transverse Peak 2. Longitudinal 3. Surface Trough Do Waves need mediums? Some waves do not need matter (called a “medium”) to be able to move (for example, through space). These are called electromagnetic waves (or EM waves). Some waves MUST have a medium in order to move. These are called mechanical waves.  LEARNING OBJECTIVES Day 2: Distinguish between longitudinal and transverse waves. Describe the relationship between the different properties of waves.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The to-and-fro movements of the wave are called oscillations. In a transverse wave these oscillations are at right angles to the direction in which the energy is travelling.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The to-and-fro movements of the wave are called oscillations. In a transverse wave these oscillations are at right angles to the direction in which the energy is travelling. 2. Longitudinal Waves Eg. sound Waves in which the medium moves back and forth in the same direction as the wave Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction In longitudinal waves the oscillations (vibrations) are backwards and forwards. The different sections are known as compressions and rarefactions.  LEARNING OBJECTIVES Day 3: Describe the relationship between the different properties of a wave Use mathematical expressions to calculate wave speed.  Think,Pair and Share. Think about the wave model with a rope. How do you think the size of the wave going through the rope is affected by how far you moved your arm up and down or how far you moved your arm back and forth? TURN and TALK  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Speed = frequency x wavelength  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Speed = frequency x wavelength (λ = Greek letter v = fλ lambda) m/s Hz m  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Example 1: a wave has a wavelength of 12m. Calculate the wave speed if it has a frequency of 20 Hz. v = fλ v = 20 x 12 v = 240 m/s  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Exercise 2: A wave has a frequency of 10 Exercise 1: a wave has a Hz, a speed of 50m/s. wavelength of 8m and a frequency Calculate the wavelength of the of 7 Hz. wave Calculate the wave speed if it has v = fλ  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. v Example 1: a wave has a Example 2: a wave has a frequency wavelength of 12m. Calculate the of 10 Hz. Calculate the wavelength wave speed if it has a frequency of f if it has a wave speed of 50 m/s. 20 Hz. v = fλ v = 20 x 12 v = 240 m/s λ v = fλ λ = v / f λ = 50 / 10 λ = 5m  Eg. light, ultra-violet, gamma Transverse Waves rays, radio.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves 1. Wavelength. The distance between any two corresponding points on the wave. (metres)  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves 1. Wavelength. 2. Amplitude. The The distance maximum between any two displacement of corresponding the wave from its points on the rest point. wave. (metres)  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves 1. Wavelength. 2. Amplitude. The 3. Speed. The The distance maximum speed of the wave between any two displacement of is measured in corresponding the wave from its metres per second points on the rest point. (m/s). wave. (metres) Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves 4. Frequency. The number of waves passing any point in one second. The unit of frequency is the hertz (Hz). One hertz is one vibration of the wave per second. The time for one oscillation is called the period.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves 4. Frequency. The number of For example, if five complete waves passing any point in waves pass a given point in one one second. The unit of second (i.e. five complete frequency is the hertz (Hz). oscillations) then the One hertz is one vibration frequency is 5 Hz. of the wave per second. The time for one oscillation is called the period.  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. Features of transverse waves Remember! The frequency (in Hz) is the number of oscillations per second. The period (in seconds) is the time for one complete oscillation. Frequency = 1 period  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Speed = frequency x wavelength (λ = Greek letter v = fλ lambda)  Eg. light, ultra-violet, gamma Transverse Waves rays, radio. The wave equation Linking together speed, frequency and wavelength. Example 1: a wave has a Example 2: a wave has a frequency wavelength of 12m. Calculate the of 10 Hz. Calculate the wavelength wave speed if it has a frequency of if it has a wave speed of 50 m/s. 20 Hz. v = fλ v = fλ λ = v / f v = 20 x 12 λ = 50 / 10 v = 240 m/s λ = 5m Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction In longitudinal waves the The oscillations in oscillations (vibrations) are longitudinal waves are in backwards and forwards. the direction of travel. The different sections are known as compressions and Sound waves are rarefactions. longitudinal waves.  Looking at Waves We can study the properties of waves by using a ripple tank.  Looking at Waves We can study the properties of waves by using a ripple tank. http://en.wikipedia.org/wiki/Ripple_tank  Looking at Waves We can study the properties of waves by using a ripple tank. Paddle vibrates to produce waves. wavefronts A ripple tank produces water waves http://en.wikipedia.org/wiki/Ripple_tank that can be reflected, refracted and diffracted.  Looking at Waves We can study the properties of waves by using a ripple tank. If a plain barrier is put in the way http://en.wikipedia.org/wiki/Ripple_tank then the waves are reflected.  Looking at Waves We can study the properties of waves by using a ripple tank. If a block is submerged in the tank then http://en.wikipedia.org/wiki/Ripple_tank the waves are refracted.  Looking at Waves We can study the properties of waves by using a ripple tank. The block makes the water more shallow which slows the waves down. If a block is submerged in the tank then http://en.wikipedia.org/wiki/Ripple_tank the waves are refracted.  Looking at Waves We can study the properties of waves by using a ripple tank. If there is a gap in the barrier then the waves will be reflected – if the gap is smaller than the wavelength of the waves. http://en.wikipedia.org/wiki/Ripple_tank  Looking at Waves We can study the properties of waves by using a ripple tank. However, if the gap in the barrier is similar in width to the wavelength of the wave, then the wavefronts are http://en.wikipedia.org/wiki/Ripple_tank diffracted.  Looking at Waves We can study the properties of waves by using a ripple tank. If the gap in the barrier is larger than the wavelength of the waves, then the wave will pass through unchanged http://en.wikipedia.org/wiki/Ripple_tank apart from slight diffraction at the edges. Looking at Waves Looking at Waves Looking at Waves Looking at Waves  LEARNING OBJECTIVES Core Supplement Demonstrate understanding that waves transfer energy without transferring matter Describe what is meant by wave motion as illustrated by vibration in ropes and springs and by experiments using water waves Use the term wavefront Give the meaning of speed, frequency, Recall and use the equation v = f λ wavelength and amplitude Distinguish between transverse and longitudinal waves and give suitable examples Describe how waves can undergo: – Describe how wavelength and gap size reflection at a plane surface – affects diffraction through a gap refraction due to a change of speed – Describe how wavelength affects diffraction through a narrow gap diffraction at an edge Describe the use of water waves to demonstrate reflection, refraction and diffraction PHYSICS – General Wave Properties