Conceptual Physics - Waves
Day 1 - 2 | Day 3 | Day 4 | Lab | Reading Assignment

This Unit's	Process Standards: 4.1, 5.1, 5.2, 5.3 Content Standards: 3.1, 3.2 Instructional Technology Standards: 4.2

Wave Transverse Longitudinal Amplitude Wavelength Frequency Hertz Reflection Refraction	Diffraction Interference Constructive Destructive Standing wave Sound Speed of sound Intensity Pitch Timbre	Acoustics Resonance Reverberation Music Noise Doppler Effect Outer ear Middle ear Inner ear

Waves:

Disturbances that transfer energy through matter or space.

What determines the speed at which a wave travels?

Types of waves:

Transverse wave
The motion of the medium is at right angles to the direction the wave is moving. Particles of the medium move up and down, but not horizontally.

Longitudinal wave

The motion of the medium is parallel to the direction the wave is moving. Particles of the medium move horizontally, but not up and down.

Examinewaves.

Wave characteristics:

Amplitude -
• The maximum distance molecules are displaced from their rest position.
• Amplitude indicates the energy of the wave.
Wavelength -
• The distance between two consecutive crests of a wave.
• Symbol for wavelength is the greek letter lambda.
Frequency -
• The number of complete waves per unit of time.
• Hertz (Hz) - The units of wave frequency.
• 1 Hz = 1 wave / sec
Wave speed -
• Wave speed depends on the medium in which it travels.
• In a given medium, the speed of a wave is constant.
• Wave speed is calculated by the equation:

Speed = (frequency) (wavelength)

Wave interactions:

Reflection
The bouncing back of a wave after it strikes a boundary.
• incident wave - the incoming wave.
• reflected wave - the wave that is bounced back.
Refraction
The bending of a wave due to a change in speed.
Diffraction
The bending of waves around the edge of a barrier.
Interference -
The interaction of two or more waves to produce a single new wave.
• Types of interference:
  • Constructive interference The crests of two waves combine.
    • Antinode - A point at which constructive interference causes maximum energy displacement.
  • Destructive interference The crest of one wave combines with the trough of another.
    • Node - A point at which destructive interference results in no energy displacement.
• Standing wave: When constructive and destructive interference produce stationary nodes and antinodes.

Computer Assignment 322:
This assignment must be completed by the end of class on tomorrow to receive credit.
Scoring criteria

1. Make a set of PowerPoint slides. These slides will be shown on the class TV and must be easily read from the back of the room.
   1. Make a slide for each of the following:
      • Slide 1 - Using PowerPoint drawing tools, draw a transverse wave. Title the slide "Transverse Wave".
      • Slide 2 - Duplicate slide 1 and label the amplitude. Title the slide "Amplitude".
      • Slide 3 - Duplicate slide 1 and label the wavelength. Title the slide "Wavelength".
      • Slide 4 - Use a single straight line to indicate a ray of light. Show this light ray striking a boundary at a 45 degree angle and reflecting. Label the incident wave and the reflected ray. Title the slide "Reflection".
      • Slide 5 - Draw a horizontal line across the slide. Label the top part of the slide as "air" and the bottom part as "water". Show a light ray entering the water at a 45 degree angle. Refraction occurs as the light ray goes from the air to the water. Correctly draw this on the slide. Title the slide "Refraction".

   Save this file on your computer.
   Show the set of slides to your science facilitator on your computer.

When everyone at your table has completed the assignment, ask your facilitator for a wave spring. Practice with the spring until you can demonstrate both constructive interference and destructive interference. Take a digital picture with the class camera that clearly shows one of these types of interference.

Day 3

Does sound travel in outer space?

Radiologic Technologist

Sound: Longitudinal waves composed of a series of compressions and rarefactions.

The speed of sound is determined by: Temperature - As the temperature of the medium increases, the speed of sound increases. Since temperature is a measure of particle motion, the higher the temperature, the faster the particles of the medium are moving. The speed of sound in air is 331.5 m/sec - at 0 oC. The speed of sound in air is 340 m/sec - at 15 oC. (the generally accepted value) The speed of sound in air is 346 m/sec - at 25 oC. Nature of the medium - Sound travels fastest in the most elastic materials. In this case, "elastic" means the material returns to its original shape quickly. In general, solids are more elastic than liquids which are more elastic than gasses. The speed of sound in water is 1500 m/sec. The speed of sound in steel is 5200 m/sec. With materials in the same phase, sound travels slower in the denser material.

Properties of sound:

Intensity -
• The amount of energy in a wave.
• Intensity determines the amplitude of a wave.
• Intensity relates to the loudness of a sound - the greater the intensity, the louder the sound.
• Decibels - the units of intensity.
  • Sounds over 120 decibels will cause pain in the ears.
  • Ear damage can begin with exposure to sounds as low as 85 decibels.
Pitch -
• How low or high the sound is.
• The frequency of a wave determines its pitch.
• Pitch is related to frequency - the higher the frequency, the higher the pitch.
• The human ear can hear sounds ranging from 20 Hz to 20,000 Hz.
• Sounds over 20,000 Hz are called ultrasonic.
  • Thunder has a low pitch with a frequency less than 50 Hz.
  • A whistle has a high pitch with a frequency close to 1000 Hz.
Timbre -
• Timbre can be described as sound quality.
• An object vibrating to produce sound is actually vibrating at several frequencies at once. The blending of these "pitches" gives a sound its timbre.
• The better these "pitches" blend, the better the sound quality.

Acoustics -
• The science of sound.
Resonance -
• The ablility of an object to vibrate by absorbing energy of its own natural frequency.
• Natural frequency - Every medium has its own vibration frequency.
Reverberation -
• A combination of many reflected waves.
Music
• Sound with a pleasing quality, a definite identifiable pitch, and a definite repeated rhythm.
Noise
• Noise has no pleasing quality, definite identifiable pitch, or definite repeated rhythm.

Outside of class with two partners, build a musical instrument that is able to produce at least four different pitches of sound. Bring the instrument to class and play a tune for the class.

Day 4

Which travel farther, high pitch or low pitch sounds?

The Doppler Effect:

• A change in the frequency and pitch of a sound due to the motion of either the sound source or the observer.
• A sound source moving toward an observer compresses the sound waves in front of it. This causes the observer to "hear" a higher frequency and pitch.
• A sound source moving away from an observer stretches the sound waves behind it. This causes the observer to "hear" a lower frequency and pitch.

Experiment with the Doppler Effect.

When do you heara supersonic airplane?

Hearing and the Human Ear:

Outer Ear:
• Ear flap - Catches sound waves and turns them into the ear canal.
• Ear canal - Funnels the waves to the eardrum.
• Eardrum - A tightly stretched membrane that vibrates as the sound waves strike it.
Middle ear:
• Hammer - A small bone touching the inside of the eardrum that begins to vibrate with the eardrum.
• Anvil - Another bone that picks up the vibrations of the hammer and passes them to the stirrup.
• Stirrup - A bone touching the membrane leading to the inner ear.
Inner ear:
• Cochlea - A coiled, fluid-filled cavity.
• This cavity contains hundreds of fibers that are attached to nerves leading to the brain.
• The motion of the fluid in the cochlea causes these fibers to send impulses to the brain, where they are interpreted as sound.

Concept Understanding: Use this PBS webpage to answer these questions. Why are the sound waves in front of a moving car pressed closer together? How does this make the car sound different as it approaches? How does the Doppler Effect relate to a sonic boom? Use the link at the bottom of the PBS page and explore the science of racing. Study this otolaryngology website. What is the purpose of the bones in the middle ear? What fills the middle ear cavity? What is a cochlear implant and who is a candidate for one? How does a perforated eardrum effect hearing? What causes the most common form of tinnitus (ringing or noise in the ear)?

Research Links:

• Wave Curriculum - Saskatchewan Education Curriculum and Instruction
• The Physics of Hearing - University of Queensland, Australia

Physical Science

Wave speed depends on the medium in which it travels.

There is no sound in outer space.
Sound waves are formed by the vibration of particles of matter. Since there is very little matter in space, the particles are too far apart to interact and form waves.

Low pitch sounds travel farther than high pitch sounds.