Waves

Group #7: McKenna Wheeler, Andrea Kang, and

Edward Turk

• Equations:

• A disturbance propagates and carries the energy.

• Time period= amount of time for a wave to complete one cycle

• Frequency can be found by waves/seconds.• One complete cycle includes one crest and

one trough.

Types of waves:

• Longitudinal: the energy (source)moves left and right, the disturbance moves in the same direction as the wave. These are sound waves. Compression zone to compression zone.

• Transverse: the source (wave) moves up and down. An ocean wave is transverse so is light.

Reflection, Refraction, Diffraction, Interference.

• Reflection happens when the waves bounce off a barrier and change direction.

• The picture to the right shows how a light wave reflects.

• Refraction: is when the wave undergoes a change in direction when changing mediums.

• We saw this in the waves lab when the wave passed over a barrier into a shallower depth from a deep depth.

• Diffraction: when the wave changes direction due to a gap or split in the barrier. The wave passes through or around a barrier.

• The smaller the split the more diffraction occurs.

• If the frequency is bigger the wavelength becomes reduced.

• Interference: this occurs when two waves meet on the same medium. Peak to Trough.

• Constructive v. Destructive interference: I. Constructive: they have the same displacement. Add them

together. II. Destructive: have displacement in the opposite direction.

Therefore, the 2 waves cancel each other out. Then both continue past each other.

After interference:• The meeting of the two waves DOES NOT alter

the individual waves once they pass over each other. This is the principle of Superposition.

Traveling v. Standing waves: Traveling waves: the wave moves or progresses across a medium. An example would be an ocean wave. The wave will pass down the rope and when it reaches the end will travel back down the rope.

• Standing wave: the waves that seem to not move because they interfere in a way that there are points of no displacement (nodes).

• Nodes= fixed points• Antinodes= the wave crest/trough that moves up and down in place.

Doppler Effect:• Anytime there is relative motion between the sources of a

sound and the receiver of it, there is a difference between actual frequency and observed frequency.

• The pitch of the ambulance siren changes as it comes closer to you.

Questions:

1. If sound travels at 330 meters per second and you hear frequency of 440hz what is the wavelength?

A. .63 mB. .75 mC. .82 mD. 6 m

2. What is the wavelength of the wave? A. Equilibrium positionB. The distance from crest to troughC. Distance from crest to crest D. Distance from crest to the third trough

3. What is the time period of the wave?A. The time for one complete cycleB. The number of cycles per minC. the seconds divided by the wavelengths

4. A bird flaps its wings 3 times per second. What is the frequency?A. 6hzB. 3hzC. 1/3hzD. 5hz

5. What is a transverse wave?A. Up and down motion B. A sideways motion C. No motion

6. When a wave passes through a slit in the barrier it…A. ReflectsB. RefractsC. Diffracts D. Diffusion

7. Explain difference between nodes and antinodes?

A. Nodes have displacement, antinodes do notB. Antinodes have displacement, nodes do notC. Both have displacementD. They resonate

8. What is the period of a 440hz sound wave?

A. .034B. .0019C. .0022D. 14

9. What change in pitch if any, occurs when a car is moving towards you?A. Higher pitchB. Lower pitchC. No change in pitch

10. If light passing through a slit causes destructive interference what happens to the light?A. Light becomes brighterB. Light becomes less brightC. Light cancels out

ANSWER KEY:1. B 330/440 because v=df 2. C 3. A4. B hz=cycles per second5. A6. C7. B8. C period= 1/frequency9. A10. C