Friday, September 27 What is diffraction?

1  What is a wave?  A wave is a disturbance that moves through matter or space.  Can carry energy from one place to another.

2.  Can the energy carried by the ocean cause damage? Explain  Yes, it can crush the rocks along the shore line.

3.  Can waves carry matter?  No  Example: a fishing bob, the bob transfers energy to nearby water molecules. The energy is then passed from molecule to molecule as the waves spread out. The wave disturbance moves outward, but the location of the water molecules hardly change at all.

4.  How are compressional waves different than transverse waves?  Compressional waves are mechanical waves that move back and forth, while transverse waves are mechanical waves that move up and down at a 90 degree angle. (Think perpendicular)

5.  How do compressional waves carry matter?  Causes particles in matter to move back and forth along the same direction.

6.  Where are the crest and the trough on transverse wave?  High point are the crest  Low points are the trough

7.  What are the six things are considered properties of waves?  Wavelength —the distance between one point on a wave the nearest point moving with the same speed and direction.  Frequency —is the number of wavelengths that pass by a point each second.

 Amplitude of a transverse wave— is half the distance between the crest and the trough. As the distance between the crest and the trough increases the amplitude increases.

 Amplitude of a compressional wave—  Depends on the density of the material in compressions and rarefactions.  Compression are more together  Rarefactions—are farter apart

Amplitude and energy—  VIBRATIONS produce energy  The more vibration the energy a wave carries the larger the amplitude.  Seismic waves—the larger the energy wave—the higher the amplitude—the more damage it can cause

Wave speed  The speed depends on the material that the wave is going through.  The faster the wave the more compressions it has.

8.  What types of waves cause the most damage during an earthquake?  Seismic wave—surface waves

9.  List three examples of electromagnectic waves.  Light, radio waves, X rays  Refer to page

10.  What types of waves are electromagnetic?  Transverse

11.  What is the wave speed equation?  Refer to yellow box at the top of the page 698.  Wave speed = wavelength multiplied by frequency  V=speed  Wave length is measured in lambda (meters)  Frequency is measured in Hz Hertz

12.  Figure out what information that you know.  Substitute into the formula  Multiply  Add units  Write sentence  1. (3.3 m/s)

13.  How can waves change direction?  Waves can change direction when they travel from one material to another.  They can bounce off each other or other materials.

14.  What does the speed of the wave depend on? Explain:  The speed of the wave depend on the properties of the material through which it travels.  Light waves travel faster than water waves

15  What is the law of reflection?  The angle that the incoming waves makes equals the angle that the outgoing wave makes.

16  What is diffraction?  The bending of waves around an object What is refraction? is the change in direction of a wave when I changes speed as it travels from one material to another.

17.  How does the diffraction of sound and light waves differ?  The wavelengths of sound waves are similar to the size objects around you, but the wave-length of light waves are much shorter.