The Behavior of Waves

1. The Behavior of Waves Chapter 10

2. Reflection • Reflection – when a wave strikes an object and bounces off of it • All types of waves can be reflected • It happens in two steps. 1. Light strikes your face and bounces off. 2. The light reflected off your face strikes the mirror and is reflected into your eyes.

3. Law of Reflection • The wave which strikes a surface is called the incident ray • The wave that bounces off of the surface is called the reflected ray Law of Reflection – the angle of incidence is always equal to the angle of reflection

4. Refraction • Refraction – the bending of waves caused by a change in its speed as it moves from one medium to another • The greater the change in its speed, the more the wave bends

5. Light passes from air to water: wave bends towards the normal because the wave is slowing down • Light passes from water to air: wave bends away from the normal because the wave is speeding up

6. Refraction of light in water • Light waves reflected • from the swimmer’s foot • are refracted away from • the normal and enter • your eyes • But, your brain assumes that all light waves have traveled in a straight line. • The light waves that enter your eyes seem to have come from a foot that was higher in the water.

7. How does a prism work? 1.) Light waves enter into prism and slow down. 2.) This causes the waves to bend 3.) The different colors of light bend different amounts so the colors are separated

8. Diffraction • Diffraction – when an object causes a wave to change direction and bend around it • After they pass through the opening, the waves spread out.

9. Diffraction and Wavelength • Amount of diffraction depends on the size of the object the waves hit and the wavelength of the waves • If the object is smaller than the wavelength the waves will bend around it • So sound waves which are larger will diffract much better than light waves which are much smaller

10. Absorption • Waves can also be absorbed when they strike an object. • Energy is converted into thermal energy • This is why wearing dark clothes in the winter months keeps you warmer

11. Interference • Interference – when two or more waves combine to form a new wave

12. Constructive Interference • Constructive interference – when two or more waves add together • In transverse waves the crests will line up with one another • In compressional waves the compressions will line up with one another • The overall effect is to increase the amplitude (energy) of the wave

13. Destructive Interference • Destructive interference – waves subtract from one another when they overlap

14. Resonance • The process by which an object is made to vibrate by absorbing the energy at its natural frequencies • Tuning forks, when struck, will vibrate at certain natural frequencies • If enough energy is absorbed, the object can vibrate so strongly that it breaks apart.

15. Standing Wave • A standing wave is a special type of wave pattern that forms when waves equal in wavelength and amplitude, but traveling in opposite directions, continuously interfere with each other • The places where the two waves always cancel are called nodes. http://electron9.phys.utk.edu/phys135d/modules/m10/waves.htm