1. WAVES

2. What is a wave? A wave is a transfer of energy through matter or through space. It is a repeating disturbance. Examples of Waves Ocean Earthquakes Light Ripples on a pond Tsunamis Sound

3. Medium The matter that waves travel through is called a medium. Mediums can be solid, liquid, gas, or a combination of these.

4. What a wave does not do... A wave does not transfer matter A wave will not last forever. A wave will only last as long as it has energy.

5. Waves can be separated into two categories M echanical Waves - can travel only through medium Electromagnetic waves - can travel through space (they do not need a medium) Mechanical waves are one of two types Transverse or compressional

6. Mechanical Waves: Transverse Waves The medium moves perpendicular to the wave direction. (90o angle) In the ocean, the water moves up and down while the wave travels horizontally. When a leaf falls on a pond, the water moves up and down while the wave moves outward

7. Mechanical Waves: Compressional Waves The medium moves in the same direction as the wave. As t he wave moves it looks as if the spring is moving from one end to the other. BUT! The spring carries only energy, not matter. Co mpressional waves are also called longitudinal waves. Sound waves are an example of a compression waves. Compressional wave video

8. Mechanical Waves: Compressional Waves The medium moves in the same direction as the wave. So und waves are an example of a compression waves. When a sound/noise is made, nearby air molecules are pushed together by the vibrations. The air molecules in the air make a compression wave similar to the spring. Sound waves can travel through other mediums such as water and wood. sound waves video 2Sound waves videosound waves video 3 Think about this! How do we "hear" sound?

9. Water Waves Water waves are not purely transverse waves. Water may move up and down as well as back and forth. Ocean waves are mainly caused by the blowing of wind.

10. Seismic Waves (pronounced SIZE-mik) Seismic waves are energy produced from breaking of the Earth's crust. A seismic wave travels outward from the disturbance as long as it has energy. Seismic waves are a combination of compressional and transverse waves.

11. Direction of wave

12. Have you been paying attention?? Let's see what you have learned 1. Which would a water wave carry? A. A boat on the surface B. The fish of the sea C. Energy D. Water molecules

13. 2. What type of waves are sound waves? A. electromagnetic B. compressional C. transverse D. water

14. 3. Which type of wave does not need a medium? A. electromagnetic B. mechanical C. ocean D. sound

15. 4. Mechanical waves can travel through space. A. True B. False

16. Parts of a Wave: Section 10.2 Waves can differ in how much energy they carry and in how fast they travel.

17. Parts of a Wave: Transverse Waves Consist of alternating high and low points. High points: Crests Low points: Troughs

18. Parts of a Wave: Transverse Waves Wavelength is the distance between one point on a wave and the nearest similar point. For a transverse wave, wavelength is the distance from crest to crest, or trough to trough.

19. Parts of a Wave: Compressional Waves Coils close together (dense area): Compression Coils less tightly packed (spread apart): Rarefaction No alternating high and low points.

20. Parts of a Wave: Compressional Waves Wavelength is the distance between one point on a wave and the nearest similar point. Fo r a compressional wave, wavelength is the distance from compression to compression, or rarefaction to rarefaction. Interesting fact: S ound waves that have short wavelengths (a few cm) are high pitched while the wavelength for deep sounds can reach up to 15m. 15m is over 49ft!

21. Parts of a Wave: Frequency and Period Frequency is the number of wavelengths that pass a certain point each second. - To find the frequency of a transverse wave, count the number of crests or troughs that pass a point each second. Fre quency of the wave = rate of vibration of the source creating the wave. Period is the amount of time it takes one wavelength to pass a point. The unit for frequency is the Hertz (Hz). The unit for period is the second (s).

22. Parts of a Wave: Wavelength, Frequency, and Period As frequency increases, period decreases As frequency increases, wavelength decreases Time 1 2 3 4 5 6 7 8 9...

23. Parts of a Wave: Speed of a Wave The speed of a wave depends on the medium through which its traveling. Sound waves travel faster in liquids and solids than in gasses. Sound waves usually travel faster through a material if the temperature is increased. To calculate the speed (v) of a wave multiply its frequency by its wavelength. speed (in m/s) = frequency (in Hz) x wavelength (in m)

24. Practice Problems A wave with a frequency of 14 Hz has a wavelength of 3 meters. At what speed will this wave travel? speed (in m/s) = frequency (in Hz) x wavelength (in m)

25. Practice Problems Sound waves in air travel at approximately 330m/s. Calculate the frequency of a 2.5m-long sound wave. speed (in m/s) = frequency (in Hz) x wavelength (in m)

26. Parts of a Wave: Amplitude of a Wave The amplitude of a wave is related to the energy carried by the wave. The greater the amplitude, the greater the energy. Amplitude for Transverse Waves Amplitude for Compressional Waves Amplitude for a transverse wave is the height from the crest to the origin (rest position) or from the trough to the origin. Amplitude for a compressional wave is measured by how tightly packed (closer) the coils are in a compression.

27. Behavior of a Wave: Reflection Reflection occurs when a wave strikes an object and bounces off of it. All types of waves can be reflected. Sound, light, water, etc. Reflection of sound waves are echoes.

28. Behavior of a Wave: Law of Reflection The law of reflection states that the angle of incidence and the angle of reflection are equal to each other. All waves obey the law of reflection. The beam striking the mirror is the incident beam. The beam bouncing off of the mirror is the reflected beam. The line drawn perpendicular to the surface of the mirror is called the normal. Angle formed by the incident beam and the normal is the angle of incidence. Angle formed by the reflected beam and the normal is the angle of reflection

29. Behavior of a Wave: Refraction Light travels slower in water than in air. Light waves slow down and bend toward the normal. What happens when light travels from water to air? Refraction occurs when a wave passes from one medium to another. Think back: What is a medium? If the wave is traveling at an angle when passes from one medium to another, it changes directions (bends), as it changes speed. W hy would the wave change speed?

30. Behavior of a Wave: Diffraction Waves diffract when going through a narrow opening, spreading out after passing through. The amount of diffraction depends on the size of the object (or opening). Waves bend around smaller objects more than larger objects. When objects are much larger than the wavelength, almost no diffraction occurs. Diffraction occurs when an object causes a wave to change direction and bend around it. Think about it: How is refraction different than diffraction? Refraction: Waves pass through an object. Diffraction: Waves pass around an object. sound waves and light waves from the cafeteria!

31. Behavior of a Wave: Interference Interference occurs when two or more waves overlap and combine to form a new wave. Note the pictures for constructive interference and destructive interference. What is the difference? Constructive interference: Crests and troughs align (same time; same place). Waves add together to form new wave. (These are called in phase; additive) Destructive interference: Crests and troughs fo not align (crests align with trough). New waves forms from the difference (subtracting) of waves. (These are called out of phase;subtractive)

32. http://tinyurl.com/refrefdif http://tinyurl.com/wavpartsrvw

33. 1. 4. 3. 7. 8.6.5. 2. REVIEW Number your note card 1-8. Use the word bank at the top to label the diagram to the right. Although you may be unfamiliar with one term you should be able to determine it by process of elimination. Turn in your note card with your name on it.