1. Waves What do you know?

2. Types of waves Mechanical – need a medium or material to travel through ex. Water, slinky Mechanical – need a medium or material to travel through ex. Water, slinky Electromagnetic- do not need materials to travel ex. Xrays, light Electromagnetic- do not need materials to travel ex. Xrays, light Waves transmit energy through space or materials Waves transmit energy through space or materials

3. Transverse Waves The wave travels perpendicular to the motion of the The wave travels perpendicular to the motion of the matter being displaced

4. Anatomy of a wave

5. Four properties of waves Four properties of waves Frequency Frequency Wavelength Wavelength Velocity Velocity Amplitude Amplitude period period

6. AMPLITUDE Distance between the normal and the top or bottom of a wave. Distance between the normal and the top or bottom of a wave. The greater the amplitude, the greater the energy of the wave or the greater the energy went in to producing a wave. The greater the amplitude, the greater the energy of the wave or the greater the energy went in to producing a wave. Ripple vs tsunami Ripple vs tsunami

7. Frequency The number of times a wave passes a point in a given time period. The number of times a wave passes a point in a given time period. Measure in hertz. Measure in hertz. 1 hz = a cycle per second 1 hz = a cycle per second

8. Wavelength The distance between 2 crests or troughs. The distance between 2 crests or troughs. Long wavelengths usually mean low frequencies Long wavelengths usually mean low frequencies

9. Period Time it takes for a cycle or disturbance to occur Time it takes for a cycle or disturbance to occur Time from crest to crest or trough to trough Time from crest to crest or trough to trough Period and frequency are determined by the source of that wave. They do not depend on the wave’s speed or the medium. Period and frequency are determined by the source of that wave. They do not depend on the wave’s speed or the medium.

10. Velocity The speed of a wave formula The speed of a wave formula Velocity = wavelength X frequency Velocity = wavelength X frequency Velocity is determined by the material that the wave is traveling through. Velocity is determined by the material that the wave is traveling through. EX. Sound travels in water at a different speed than in air. EX. Sound travels in water at a different speed than in air. Temp and viscosity can effect velocity. Temp and viscosity can effect velocity.

11. Speed Sound travels at 343 m/s in air. Sound travels at 343 m/s in air.

12. Ex. problems A sound wave has a frequency of 262 Hz and a wavelength of 1.29m. What is the speed of the wave? A sound wave has a frequency of 262 Hz and a wavelength of 1.29m. What is the speed of the wave?

13. Longitudinal wave Particles vibrate parallel to the motion of a wave as in earthquakes. Particles vibrate parallel to the motion of a wave as in earthquakes. Compressions Compressions rarefactions rarefactions

14. Longitudinal waves Waves transmitted in fluids and air are longitudinal Waves transmitted in fluids and air are longitudinal This includes sound and water waves This includes sound and water waves Water waves at the surface of water have both longitudinal and transverse characteristics. These are known as surface waves. Water waves at the surface of water have both longitudinal and transverse characteristics. These are known as surface waves.

15. What happens to waves when they hit a barrier or change mediums. Reflection Reflection Refraction Refraction Diffraction Diffraction

16. Reflection All or part of a wave bounces back or returns All or part of a wave bounces back or returns The approaching wave is the incident wave The approaching wave is the incident wave

17. What happens when a wave hits a more rigid barrier. The reflected waves comes back inverted or upside down. The reflected waves comes back inverted or upside down.

18. What happens when a wave enters a less rigid medium? The reflected wave returns right side up or erect. The reflected wave returns right side up or erect.

19. Law of Reflection Normal is perpendicular to surface of a barrier Normal is perpendicular to surface of a barrier

20. Constructive interference

21. Destructive interference

24. Polarization of a wave

25. Effect of a polarizer on reflection from mud flats. In the picture on the left, the polarizer is rotated to transmit the reflections as well as possible; by rotating the polarizer by 90° (picture on the right) almost all specularly reflected sunlight is blocked. specularly reflectedspecularly reflected

27. Polarizing film

29. Sound Waves Longitudinal Longitudinal Their amplitude is measured in decibels. Their amplitude is measured in decibels. This is a measure of their loudness. This is a measure of their loudness. Their frequency is heard as its pitch. Speed in air is 343 m/s.

30. Resonance Resonance is usually associated with sound waves. Resonance is usually associated with sound waves. This occurs when the vibrations of one object are picked up by another and it vibrates in sync. This occurs when the vibrations of one object are picked up by another and it vibrates in sync.