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WAVES: basics

WAVES: basics. Chapters 25.1-25.8; 26. Simple Harmonic Motion. The equal or balanced back and forth or side to side motion of a particle that is caused to vibrate by a disturbance. Similar to a pendulum’s motion. http://www.physics.uoguelph.ca/tutorials/shm/Q.shm.html.

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WAVES: basics

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  1. WAVES: basics Chapters 25.1-25.8; 26

  2. Simple Harmonic Motion • The equal or balanced back and forth or side to side motion of a particle that is caused to vibrate by a disturbance. • Similar to a pendulum’s motion. • http://www.physics.uoguelph.ca/tutorials/shm/Q.shm.html

  3. WHAT IS A WAVE? • A repeating disturbance that causes vibrations and transmits energy through matter or space.

  4. WHAT IS THE PURPOSE OF A WAVE? • To transmit energy from one place to another.

  5. WHAT HAPPENS TO ENERGY AS THE WAVE TRAVELS? • Energy is transferred from one particle to the next. • The motion of particles in a medium is like the motion of masses on a spring. • Energy of the wave spreads away from the disturbance or vibration (see white board)

  6. IS MATTER TRANSMITTED WITH THE WAVE? • No, only energy is transmitted. • The particles in the matter vibrate as the wave passes, but do not travel with the wave. • http://www.infoline.ru/g23/5495/Physics/English/waves.htm • http://members.aol.com/nicholashl/waves/movingwaves.html

  7. ARE THERE DIFFERENT TYPES OF WAVES? • Mechanical Waves • Non-Mechanical Waves microwaves Sound waves

  8. Mechanical Waves • Waves that can only travel through matter • Examples: sound, water and seismic waves • In general, mechanical waves travel fastest through solids, then slower through liquids and slowest through gases • Can be transverse or longitudinal (or compressional)

  9. Non-Mechanical Waves • Waves that can travel through matter or space (a vacuum) • Example: electromagnetic radiation (waves) or light • In general, non-mechanical waves travel fastest through a vacuum, then slower through gases, then liquids and slowest through solids • Two perpendicular transverse waves

  10. Electromagnetic Wave http://www.nrc-cnrc.gc.ca/obj/inms-ienm/images/research_images/optical_comb/COMBFIG1.gif

  11. Wave Speed • Wave speed (depends upon the composition and character of the medium it travels through)

  12. Two types of waves based upon direction of vibrating particles: • Transverse Waves cause particles in matter to vibrate perpendicular to the direction of wave travel. • Longitudinal Waves cause particles in matter to vibrate in the same direction of wave travel. • http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

  13. TRANSVERSE WAVE crest One wavelength amplitude Rest position trough

  14. Compressional (or longitudinal) Wave Rarefaction (less dense) Compression (more dense) one wavelength

  15. Wave Characteristics • Frequency (f) (the number of vibrations that occur in a given time) • Hertz (Hz) (# of vibrations per second) • High frequency waves produce waves with short periods and short wavelengths • Period (P) (the time it takes for one wave cycle to pass) • Seconds (s) • The lower the frequency, the longer the period

  16. Wave Characteristics • Wavelength λ (lambda) (the distance between one point on a wave to the next identical point; crest to crest, for example) • Meters (m) • The lower the frequency, the longer the wavelength • Amplitude (longitudinal waves—the tightness of the compression; transverse waves—the distance from the crest to rest position or from trough to rest position) • Meters (m) • The greater the amplitude of the wave, the more energy the wave transfers.

  17. Frequency vs. Intensity • Rate of vibration (frequency) • Amount of energy (intensity)— • Amplitude (amount of displacement) • loudness (relative intensity of sound) • brightness (number of photons of light) Turn up the volume--same frequencies, different intensity

  18. Why do waves become less intense away from the source? • Same amount of energy is spread out over greater and greater distances. • Same energy at every point along a wave front. • Also, simple harmonic motion of the particles can be dampened (or absorbed or transferred) by the medium (rubber, clay, springs, fluids in shock absorbers)

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