AP Physics Waves Poster

AP Physics 1

Waves

A wave is often described as a disturbance that travels through a medium from one location to another location.

Wave characteristics

Wavelength: the length of one complte wave cycle (crest to crest or trough to trough).

Frequency: the number of complete vibrational cycles of a medium per a given amount of time, or, how often the particles of the medium vibrate when a wave passes through a medium.

Waves can be categorized on the basis of their ability or inability to transmit energy through a vaccum.

Mechanical Waves

Electromagnetic Waves

LIGHT

capable of trasnmitting eenrgy through a vacuum

incapable of transmitting energy through a vaccum

Waves can also be categorized based on the direction of movement of individual particles

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Transverse Waves

LIGHT

Longitudinal Waves

particles of medium move in a direction perpendicular to the direction that wave moves

particles of medium move in a direction parellel to the direction that wave moves

TRANSVERSE WAVE DIAGRAM

SPEED EQUATIONS & RELATIONSHIPS

Equations:

• distance/time (D/T)
• wavelength/period
• wavelength*frequency

The speed of sound entirely dependent on the properties of the medium. The speed of a wave cannot be altered by changing the wavelength or frequency. For instance, if the wavelength of of a wave increases, the frequency will decrease proportionally, resulting in no change in speed.

SOUND

What is sound? the transfer of energy (kinetic energy) from a vibrating object in waves that travel through matter.

How does sound travel?

All sounds begin with vibrating matter. Vibrating matter pulses against air particles next to it, causing them to vibrate and alternately push together and spread apart. (EX: SPEAKER, shown to the right)

Reflection & Diffraction

When a wave encounters an obstacle in its path, it may behave in a variety of ways.

Diffraction occurs when the direction of waves change as they passes through an opening or around a barrier in their path.

Reflection occurs whem a waves bounce back from a surgcae back toward the source

How does the Medium Impact the Speed of Sound?

The speed of sound varies depending on the medium through which it passes. Since sound is the transfer of energy between vibrating molecules, the closer the molecules are to each other and the tighter the bonds, the less time it takes for sound to travel. A variety of other factors influence the velocity of a sound wave, including elasticity, density, and temperature of the medium.

Density

Elasticity

Temperature

Density is the mass of a substance per volume. Mediums with higher densities will transmit sound slower since it takes more energy to vibrate large particles than small ones.

Elasticity refers to the tendency of a material to maintain its shape. Sound will travel faster through mediums with higher elastic properties since particles will have stronger attractions to each other.

Like sound, heat is a form of kinetic energy. Particles with higher temperatures will have more energy and thus vibrate faster, allowing sound waves to travel more quickly. Put simply, the speed of sound is faster when temperatures are higher.

The Doppler Effect

What is it? The Doppler Effect is a phenomenon observed when the source of sound waves is moving with respsect to an observer. Whenever a source is approaching an observer, an apparent upward shift in frequency is perceived by the observer; when the source is receding, an apparent downward shift in frequency is perceived by the observer.

Example:

The concept is best illustrated in the case of emergency vehicle sirens. When a police car is approaching you with sirens on, for instance, the pitch of the siren is high. However, as the car recedes, the pitch of the siren decreases.

WHY does this occur?

The Doppler Effect occurs because the distance between the source and the observer is constantly changing while the source of the sound continues to emit the same frequency. Since the frequency remains the same, the same number of waves must fit between the source and the observer for a certain period of time. Therefore, when the distance between the source and the observer is decreasing, the sound waves get compressed, resulting in an apparent increase in frequency (higher pitch). Likewise, when the distance between the source and the observer is increasing, sound waves stretch apart, resulting in an apparent decrease in frequency (lower pitch).

Elasticity

ELECTROMAGNETIC SPECTRUM

7 Types of EM Waves

MICROWAVE

INFRARED

VISIBLE

RADIO

Frequency Range: 10^13 Hz – 10^14 Hz Uses: electrical heaters, cookers for cooking food, short-range communications (remote controls)

Frequency Range: 3*10^11 Hz – 10^13 Hz Uses: radar, cooking,

Frequency Range: < 3*10^11 Hz Uses: communication (broadcasting television/radio), satellite trasmissions

Frequency Range: 4 Hz – 7.5*10^14 Hz Uses: sight, lasers for surgery, TV/phone screens

ULTRAVIOLET

GAMMA

X-RAYS

Frequency Range: 10^15 Hz – 10^17 Hz Uses: industrial processes, medical/dental practices, suntanning

Frequency Range: 10^17 Hz – 10^20 Hz Uses: checking for fractured bones, mammograms

Frequency Range: 10^20 Hz – 10^24 Hz Uses: radiotherapy, sterilization and disinfection, nuclear industry

Speed of EM Waves in a Vaccum

An EM wave transports its energy through a vacuum at a speed of 3.00 x 10^8m/s

Sources

• “The Physics Classroom Website.” The Physics Classroom, www.physicsclassroom.com/mmedia/waves/em.cfm.
• “Physics Tutorial: The Speed of a Wave.” The Physics Classroom, www.physicsclassroom.com/class/waves/Lesson-2/The-Speed-of-a-Wave.
• “Physics Tutorial: The Electromagnetic and Visible Spectra.” The Physics Classroom, www.physicsclassroom.com/class/light/Lesson-2/The-Electromagnetic-and-Visible-Spectra.
• “Physics Tutorial: Visible Light and the Eye's Response.” The Physics Classroom, www.physicsclassroom.com/class/light/Lesson-2/Visible-Light-and-the-Eye-s-Response.
• Admin. “Electromagnetic Spectrum - Definition, Characteristics, Range, Diagram.” BYJUS, BYJU'S, 13 Oct. 2020, byjus.com/jee/electromagnetic-spectrum-and-electromagnetic-waves/.
• “Physics Tutorial: Reflection, Refraction, and Diffraction.” The Physics Classroom, www.physicsclassroom.com/class/sound/Lesson-3/Reflection,-Refraction,-and-Diffraction
• “The Speed of Sound in Other Materials.” Nondestructive Evaluation Physics : Sound, www.nde-ed.org/Physics/Sound/speedinmaterials.xhtml.
• “Physics Tutorial: The Doppler Effect and Shock Waves.” The Physics Classroom, www.physicsclassroom.com/class/sound/Lesson-3/The-Doppler-Effect-and-Shock-Waves.