1 / 20

Chapter 6

Chapter 6. WAVES Dr. Babar Ali. CHAPTER OUTLINE. CONCEPT OF WAVES. A wave is a disturbance that propagates through a system transferring energy Waves transfer E! (courtesy of Dr. Dan Russell, Kettering Univ.). WAVE PROPERTIES. Crest:. the highest point on a wave. Trough:.

dorian-phelps
Télécharger la présentation

Chapter 6

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 6 WAVES Dr. Babar Ali

  2. CHAPTER OUTLINE

  3. CONCEPT OF WAVES • A wave is a disturbance that propagates through a system transferring energy • Waves transfer E! (courtesy of Dr. Dan Russell, Kettering Univ.)

  4. WAVE PROPERTIES Crest: the highest point on a wave Trough: the lowest point on a wave Amplitude: maximum displacement in a wave height of crest or depth of trough Amplitude is related to the E of a wave

  5. WAVE PROPERTIES Wavelength (λ): distance between 2 successive crests Units = m or cm Frequency (f): # of waves produced per unit time. Units = 1/s = Hz Period (T): # of seconds per unit wave.

  6. WAVE SPEED • The speed of a wave can be calculated from its frequency (f) and wavelength (λ). f × λ = s • Units: Note, s = constant for a given wave

  7. Example 1: A sound wave has a speed of 344 m/s and a wave-length of 0.5 m. What is the frequency of this wave? f = ??? λ = 0.5 m s = 344 m/s f = 688 Hz

  8. Example 2: A sound wave has a speed of 344 m/s has a frequency of 20 kHz. What is this wave’s wavelength? f = 20 kHz λ = ??? s = 344 m/s λ = 0.017 m

  9. Example 3: An ocean wave passes a point on the pier at the rate of 12 waves per minute. What are the frequency and period of this wave? # of cycles = 12 time = 60 s f = ??? T = ??? f = 0.2 Hz T = 5 s

  10. LONGITUDINALWAVES • Waves where direction of particle movement is parallel to the direction of wave velocity, are longitudinal waves • Longitudinal waves have areas of high particle density (compressions) and of low particle density (rarefactions) • Sound is the most common example of a longitudinal wave.

  11. TRANSVERSEWAVES • Waves where the direction of particle movement is perpendicular to the direction of wave velocity, are transverse waves • i.e. mechanical waves, electromagnetic waves (light, microwave, x-rays, etc.)

  12. ELECTROMAGNETICWAVES • Electromagnetic waves (e&m waves) are transversewaves caused by vibrating electrons (e-) • Formed through interaction of electric and magnetic fields that are perpendicular to one another • In vacuum, e&m waves travel at the same speed and differ from each other only in freq.

  13. ELECTROMAGNETICSPECTRUM • The classification of electromagnetic waves according to their frequency is called electro-magnetic spectrum. • e&m waves range from γ rays (short λ , high f) to radio (long λ, low f)

  14. SOUND WAVES • Sound is the most common example of a longitudinal wave • In sound waves, the molecules of air transmit the vibrations through compressions and rarefactions • Sounds waves cannot travel in vacuum!

  15. SPEED OF SOUND • Speed of sound is affected by: • wind conditions, temperature, humidity and type of medium • NOT affected by its loundness (amplitude) • Sound travels faster in liquids and solids compared to gases • Closely packed molecules in solids and liquids will transmit the vibrations faster than in gases • Sound travels faster at higher T • Faster moving air particles bump into each other more frequently and carry vibrations in shorter time

  16. DOPPLER EFFECT • Pitch of a sound is the subjective measure of its frequency • High frequency sounds have high pitch, and low frequency sounds have low pitch • The apparent shift in pitch of sound when the source is moving relative to the observer is called the Doppler Effect • i.e. The sudden change in pitch of an ambulance siren as it goes by an observer is the result of the Doppler effect

  17. STANDING WAVES • Waves that are reflected on themselves and appear to “stand” are called standing waves • Standing waves produce the variety of sounds in musical instruments! (Animation) violin

  18. RESONANCE • Every object has natural vibrations caused by motion of its molecules • When a forced vibration matches an object’s natural vibrations, a dramatic increase in amplitude occurs  This phenomena is called Resonance • Some Examples • Tacoma Narrows Bridge • Resonant Bridge

  19. THE END

  20. Some Symbols Used •  all •  there is or there exists • D Change •  infinity •  multiplication •  proportional to •  less than or equal to •  greater than or equal to •  plus or minus •  degrees •  therefore • ≈ approximately equal to •  decreases •  increases • λ – Wavelength • E – Energy • H – Heat • # - Number • e- - electron • p+ - proton

More Related