Vibrations & Waves Chapter 25 Time for one swing=PERIOD How many swings/second= FREQUENCY

Check Your Understanding 6. In problem #5, the period of swing is __________. a. 0.5 secondb. 1 secondc. 2 second 7. A period of 5.0 seconds corresponds to a frequency of ________ Hertz. a. 0.2b. 0.5c. 0.02d. 0.05e A common physics lab involves the study of the oscillations of a pendulum. If a pendulum makes 33 complete back-and-forth cycles of vibration in 11 seconds, then its period is ______. 9. A child in a swing makes one complete back and forth motion in 3.2 seconds. This statement provides information about the child's a. speed b. frequecy c. period 10. The period of the sound wave produced by a 440 Hertz tuning fork is ___________. 11. As the frequency of a wave increases, the period of the wave ___________. a. decreases b. increases c. remains the same

Vibrations & Waves Chapter 25 A disturbance that carries energy from one location to another location.

Why should you know about waves? Waves are the key to sound and color. Mobile phone signals, microwave ovens all use energy carried by waves. Earthquakes and tsunamis are destructive waves of energy.

WAVES A medium is a substance or material which carries the wave. Ex. Air, water, glass, vacuum

How do waves transmit energy? As energy passes from one particle to the next, a wave transfers energy through the medium.

Types of Waves: Longitudinal wave particles of the medium move in a direction parallel to the direction which the wave moves. Example: Sound

How Sound Waves are Produced

Types of Waves: Longitudinal wave COMPRESSION RAREFACTION COMPRESSION AMPLITUDE WAVELENGTH

Parts of waves: Sound Wavelength-distance from one wave to the next Amplitude-size of each wave. WAVELENGTH AMPLITUDE

Types of Waves Transverse wave particles of the medium move in a direction perpendicular to the direction which the wave moves. Example: Light

Types of Waves Transverse wave CREST TROUGH WAVELENGTH AMPLITUDE

Frequency How often the particles of the medium vibrate when a wave passes through the medium. Example: 2 cycles/second or 2 Hertz (Hz) Frequency refers to how often something happens

Period The period of a wave is the time for a particle in a medium to make one complete cycle. measured in units of time such as seconds, hours, days or years. Check your understanding TIME—not distance!

1.A wave is introduced into a thin wire held tight at each end. It has a frequency of 51.2 Hz. Determine the period of such a wave. Check Your Understanding 3. A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ________ Hz. a. 5.0b. 0.20c. 0.12d Frieda the fly flaps its wings back and forth 121 times each second. The period of the wing flapping is ____ sec. T =.02 Seconds T =.008 Seconds D, Convert to seconds!

Velocity of Waves Speed = Frequency x Wavelength (m/s)(Hertz)(meters) v = f x λ

MediumWavelengthFrequencySpeed Zinc, 1-in. dia. coils 1.75 m2.0 Hz_________ Zinc, 1-in. dia. coils 0.90 m3.9 Hz_________ Copper, 1-in. dia. coils 1.19 m2.1 Hz_________ Copper, 1-in. dia. coils 0.60 m4.2 Hz_________ Zinc, 3-in. dia. coils 0.95 m2.2 Hz_________ Zinc, 3-in. dia. coils 1.82 m1.2 Hz_________

Answers Multiply the frequency by the wavelength to determine the speed. Row 1: speed = 3.5 m/s Row 2: speed = 3.5 m/s Row 3: speed = 2.5 m/s Row 4: speed = 2.5 m/s Row 5: speed = 2.1 m/s Row 6: speed = 2.2 m/s

CAN YOU GET THEM TO SAY IT?? Wave Characteristics & Wave Interactions

Wave Characteristics Rarefaction Wavelength Trough Transverse Period

Wave Characteristics Frequency Compression Amplitude Longitudinal Crest

Wave Interactions Doppler Effect Resonance Destructive Interference Reflection Medium

Wave Interactions Refraction Natural Frequency Red Shift Angle of Reflection Constructive Interference

How Light is Produced A photon of light is produced whenever an electron in a higher-than- normal orbit falls back to its normal orbit. The frequency, or color, that exactly matches the distance the electron falls.

Light Waves Light (electromagnetic waves) are waves which are capable of traveling through a vacuum Produced by a vibrating electric charge Consist of both an electric and a magnetic component. Page 643 in book

(On Handout)

WAVE INTERACTIONS

Wave Interactions Doppler Effect the shift in frequency and wavelength of waves which results from a source moving Click picture to hear car.

Interference Wave interference occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape which results from the net effect of the two individual waves.

Wave interference

Interference Constructive interference Destructive interference

Wave interference: Standing Waves A standing wave pattern is a pattern which results from the interference of two or more waves along the same medium.

Reflection The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.

Refraction Refraction is the bending of a wave when it enters a medium where it's speed is different.

Refraction is the phenomenon which makes image formation possible by the eye as well as by cameras and other systems of lenses. Refraction in Eye Refraction in Camera Image is on retina. Image is on film.

DIFFRACTION Waves can `bend,' or diffract, around corners. An example of diffraction: if you speak into one end of a cardboard tube, the sound waves emerging from the other end spread out in all directions… rather than traveling in a straight line like a stream of water from a garden hose. CAN RESULT IN INTERFERENCE!

RESONANCE when one object vibrating at the same natural frequency of a second object forces that second object into vibrational motion. Swinging a child in a playground swing is an easy job because you are helped by its natural frequency.

Now You See It… Journal # 23 May 23, )Get a cup, piece of tape, & penny from the front table. 2)Tape a penny to the inside bottom of the Styrofoam cup and place it on the table. 3)Move your head down so that the penny just disappears behind the rim of the cup. Hold your head steady so that the penny is still hidden to your eye. 4)Have another student pour water into the cup. What happens? Draw a picture.