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WAVES

WAVES. Physical Science Chapter 11. Wave Medium Mechanical wave Electromagnetic wave Transverse wave Longitudinal wave Crest Trough Amplitude Wavelength. Period Frequency Wave Speed Doppler Effect Pitch Reflection Diffraction Refraction Interference Standing wave.

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WAVES

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  1. WAVES Physical Science Chapter 11

  2. Wave Medium Mechanical wave Electromagnetic wave Transverse wave Longitudinal wave Crest Trough Amplitude Wavelength Period Frequency Wave Speed Doppler Effect Pitch Reflection Diffraction Refraction Interference Standing wave Vocabulary Chapter 11 Define these words and study for a vocabulary test.

  3. Types of Waves • Wave – A disturbance that caries energy through matter or space. • Medium – Matter through which a wave travels. • Mechanical wave – Waves that require a medium to pass the energy through. • Electromagnetic wave – (Light, radio, infrared, x-ray, etc) Do not need a medium to pass through. They are caused by a disturbance in electric and magnetic fields.

  4. Supernumerary rainbow A rainbow is an example of electromagnetic waves of visible light. The colors of the spectrum can be seen in a rainbow. ROYGBIV

  5. Waves Transfer Energy • Energy is the ability to do work, so waves carry energy and do work. • Work is done when a force causes a change in motion of an object. • Water waves do work on a leaf, a boat, or on a beach. How? • Sound waves do work on your eardrum. How? • Light waves do work on your eye or photographic film. How? • Energy may be spread out as a wave travels. • Each circle of the wave is called a “wave front”.

  6. Vibrations and Waves • Waves are related to vibrations. • Most waves are created by a vibrating object. • Electromagnetic waves may be caused by vibrating charged particles. • In mechanical waves, particles in the medium vibrate as the wave passes through the medium.

  7. More on Vibrations • Simple harmonic motion: The motion is periodic, as it repeats itself at standard intervals in a specific manner Damped harmonic motion: A vibration that fades out as energy is transferred from one object to another.

  8. Transverse waves: the particles of the medium vibrate perpendicular to the direction of the wave. A good example would be a stadium wave. The people would be moving at a right angle to the direction of the wave. Light waves are transverse waves. The electric and magnetic fields are perpendicular to the direction the light travels. Longitudinal waves: the particles of the medium vibrate parallel to the direction of the wave. Sound waves are a good example of a longitudinal wave. Transverse and Longitudinal Waves

  9. Surface Waves • Particles move in a circular motion. • Water waves are an example of a surface wave. • The particles in a surface wave move both perpendicular and parallel to the direction of the wave.

  10. Wave Properties • All transverse waves have a similar shape. It’s called a sine curve. • Waves with this shape are calledsine waves. crest wavelength amplitude wavelength trough

  11. Wave properties continued…. • Amplitude – the greatest distance that particles in a medium move from their normal position. • Wavelength – the distance between two equivalent parts of a wave. The symbol is the Greek letter Lambda, λ • Period – the time required for one full wavelength to pass a certain point. Represented by the symbol T, expressed in seconds. • Frequency – the number of waves that pass a given point in one second. The symbol for frequency is f, it is measured in Hertz. One vibration per second is 1Hz. • f = 1/T

  12. Electromagnetic Spectrum

  13. Visible Light Our eyes can detect light with the frequencies ranging from 4.3 x 1014 Hz to 7.5 x 1014 Hz.

  14. ROYGBIV WAVES Cones in our eyes are receivers for these tiny visible light waves. The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed.

  15. Wave Speed • Wave speed is simply how fast a wave moves. • Recall the formula for speed s = d/t • So the formula for wave speed is as follows: speed = wavelength / period Or V = λ / T Wave speed can also be calculated by multiplying frequency times wavelength or V = f x λ

  16. Practice the math… Given: Frequency, f = 264 Hz Wavelength, λ = 1.30 m Unknown: wave speed v = _______m/s 343 Reverse the formula you just used and show the formula for frequency. ________ F = v / λ

  17. Wave speed continued…. • The speed of a wave depends on the medium. • Sound waves travel 340m/s in air. • They travel 3 to 4 times faster in water. • Through rock or metal they travel 15 to 20 times faster than in air. • Why??? The arrangement of particles in a medium determines how well a wave travels through it. Kinetic theory explains this. Molecules of gases are further spread apart then liquids or solids.

  18. The speed of light • Light has a finite speed. • 186,000 mi/s • 3 x 103 m/s • All electromagnet waves travel at this speed in empty space. • The speed of light is represented by the symbol c. • Light waves will travel slower when passing through a medium such as water or air.

  19. The Doppler Effect • Pitch – how high or low the sound is. • Pitch is determined by frequency. • The higher the frequency the higher the pitch and vice versa. • Frequency changes if the source is moving. • This change in frequency based on movement is called the “Doppler Effect”.

  20. Wave Interactions • Reflection – The bouncing back of a wave when it reaches a surface or boundary. • Diffraction – the bending of waves as they pass an edge. • Refraction – The bending of waves as they pass from one medium to another. • Interference – when two waves arrive at the same location at the same time they combine to form a new wave. • Constructive interference – When the crest of one wave overlaps the crest of another and they are added together to make a larger wave • Destructive Interference – When the crest of a large wave meets the trough of another smaller wave and they combine by subtraction. Two waves of the same size may completely cancel each other out. The amplitudes must be the same.

  21. Standing Waves • Standing Wave – A wave form caused by interference that appears not to move along the medium. • Nodes – Regions of no vibration, where crest of one wave meets the trough of another and causes complete destruction. • Antinodes – Regions of maximum vibration, where crests of one wave lines up perfectly with the crest of a reflected wave causing maximum constructive interference.

  22. Keep up with your notes!!! Notes test coming soon... Remember to attend the pre-test study session

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