# An Intro to Waves Hz are units of: A. amplitudeB. frequency C. periodD. wavelength In a sound wave, rarefactions are areas of: A. high amplitude B. low.

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An Intro to Waves Hz are units of: A. amplitudeB. frequency C. periodD. wavelength In a sound wave, rarefactions are areas of: A. high amplitude B. low amplitude C. high pressure D. low pressure

An Intro to Waves Hz are units of: A. amplitudeB. frequency C. periodD. wavelength In a sound wave, rarefactions are areas of: A. high amplitude B. low amplitude C. high pressure D. low pressure

An Intro to Waves Hz are units of: A. amplitudeB. frequency C. periodD. wavelength In a sound wave, rarefactions are areas of: A. high amplitude B. low amplitude C. high pressure D. low pressure

Sound Speed and Frequency: Learning Goal The student will be able to explain the nature between the speed of sound in various media and the particle nature of the media and explain selected natural phenomena (echolocation, infrasound/ultrasound) with reference to the characteristics and properties of waves (E3.5, E3.6).

Sound Speed and Frequency 3U Physics

The Speed of a Wave As demonstrated by the slinky waves, the speed at which a wave propagates is dependent on the properties of the medium.

Sound Waves Remember that sound is a pressure wave. A vibration (e.g. of a tuning fork) bumps air particles, which bump the air particles next to them, etc.

Sound in Air Sound travels faster in warmer air (in which the particles are faster-moving):

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Air: Example Example: You see a flash of lightning from a storm 1.4 km away and hear the crack of lightning 4.0 s later. What is the temperature of the air?

Sound in Liquids and Solids And sound will also travel faster in denser materials (liquids and solids). E.g. the speed of sound in water is typically 1500 m/s.

Sound in Liquids and Solids And sound will also travel faster in denser materials (liquids and solids). E.g. the speed of sound in water is typically 1500 m/s. A swimmer 1500 m away from a loud sound would hear it the sound 1 s later through the water or more than 4 s later through the air.

Echolocation: Example Example: A dolphin sends out a pulse at a frequency of 100 000 Hz and hears an echo back from an object 2.4 s later. How far away is the object?

Echolocation: Example Example: A dolphin sends out a pulse at a frequency of 100 000 Hz and hears an echo back from an object 2.4 s later. How far away is the object?

Echolocation: Example Example: A dolphin sends out a pulse at a frequency of 100 000 Hz and hears an echo back from an object 2.4 s later. How far away is the object?

Echolocation: Example Example: A dolphin sends out a pulse at a frequency of 100 000 Hz and hears an echo back from an object 2.4 s later. How far away is the object?

Frequency The frequency of any sound wave is always the frequency of the source and does not change or affect the speed of the wave as it propagates. Frequency of a wave is how many cycles/peaks pass a point in a second

Frequency The frequency of any sound wave is always the frequency of the source and does not change or affect the speed of the wave as it propagates. (Changing the speed will change the wavelength, not the frequency.)

Wavelength Distance between two similar points in successive identical cycles in a wave Distance between two similar points in successive identical cycles in a wave

The Wave Equation How are frequency, wavelength and velocity of a wave connected? How are frequency, wavelength and velocity of a wave connected? V=d/t, we can substitute λ for d, so V= λ/t and t is the period of a wave, T therefore V=d/t, we can substitute λ for d, so V= λ/t and t is the period of a wave, T therefore V= λ/T V= λ/T V= λf V= λf

Frequency Humans can hear sounds between about 20 and 20 000 Hz (though most humans lose the ability to hear very high frequencies by the time they are teenagers). Most human speech is between 200 and 8000 Hz, and the ear is most sensitive to frequencies between 1000 and 3500 Hz.

Ultrasound Sound above 20 000 Hz is called ultrasound. A common use of ultrasound is range finding under water: i.e. echolocation or sonar.

Ultrasound Diagnostic medical ultrasonograms work on the same principle.

Infrasound Sound below 20 Hz is called infrasound, which may be produced by events such as earthquakes. Some animals such as elephants use infrasound for communication, even over long distance.

Infrasound While humans cannot consciously detect infrasound, they may still be sensitive to the vibrations: In particular, infrasound is known evoke feelings of awe and fear, and frequencies close of 18 Hz, the resonant frequency of the eye, may cause optical illusions of “ghosts.” Infrasound may be responsible for many alleged “hauntings.”

Frequency and Pitch Within the audible range, frequency of a sound wave is commonly referred to as the pitch of the sound. A high-frequency sound wave has a high pitch. A high-frequency sound wave has a high pitch. A low-frequency sound wave has a low pitch. A low-frequency sound wave has a low pitch.

Frequency and Noise A sound wave of a single frequency will be heard as a distinct tone or note. Irregular sound waves will be heard as noise.

More Practice Sound Speed Quick Lab Homework: Sound Speed and Frequency

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