Waves & Sound Ch 10 6 th grade

What forms mechanical waves? A wave is a disturbance involving the transfer of energy from place to place. Waves that need a medium to travel through are called mechanical waves. Mechanical waves form when a source of energy causes a medium to vibrate. An introduction to waves

What are the types of mechanical waves? The three types of mechanical waves are transverse, longitudinal, and surface. A wave that vibrates the medium perpendicular to the direction in which the wave travels is called a transverse wave.

Transverse waves forms high and low points called crests and troughs. The rest point is the middle of each of the crests and troughs. file:///C:/Users/cpichon/AppData/Local/Te mp/wave-on-a-string_en.htmlfile:///C:/Users/cpichon/AppData/Local/Te mp/wave-on-a-string_en.html

Longitudinal waves move parallel to the wave’s motion. This causes the spacing between the coils to vary: either close together (compressions) or spread apart (rarefactions). Surface waves are a combination of transverse and longitudinal waves that travel along a surface that separates two mediums. Most common is on the surface of oceans causing up and down movement as well as circular movement. Waves 1

What are the properties of waves? Amplitude describes the height of a transverse wave’s crest or the depth of its trough from the resting point. The greater the amplitude, the higher the distance. The amplitude of a longitudinal wave is a measure of how compressed or rarefied the medium becomes. The greater the amplitude, the more dense the compression. The greater the energy the wave has, the greater its amplitude. file:///C:/Users/cpichon/AppData/Local/Temp/wave-on-a-string_en.html

The distance between two corresponding parts of a wave is its wavelength.

The frequency of a wave is the number of waves that pass a given point in a certain amount of time. Frequency is measured in units called hertz (Hz) file:///C:/Users/cpichon/AppData/Local/Temp/wave-on-a-string_en.html The speed of a wave is how far the wave travels in a given amount of time. The speed is found by dividing the distance by the time, so the unit is m/s

How are properties related? The speed, wavelength, and frequency of a wave are related by a mathematical formula! Speed = wavelength (frequency) The speed of a wave remains constant if the medium, temperature, and pressure do not change. 4 Characteristics of a Wave A Level Physics

Properties of Waves All waves have amplitude, wavelength, frequency, and speed. Properties of Waves Wavelength TRANSVERSE WAVE Crest Rest position Trough Direction of wave LONGITUDINAL WAVE Compression Amplitude Rarefaction Wavelength

What changes the direction of a wave? Reflection When a wave hits a surface, any part of the wave that cannot pass through the surface bounces back. Light reflects off of a mirror and echoes bounce off of walls.

Refraction When a wave enters a new medium at an angle, one sides of the wave changes speed before the other side. This causes the wave to bend because different parts of the wave travel at different speeds No bending occurs when the angle is 90° nor if the speed does not change in the new medium. A prism can refract light into the different wavelengths.

Diffraction When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.

Experiments on refraction, reflection and total internal reflectionExperiments on refraction, reflection and total internal reflection Reflection Refraction Diffraction

What are the two types of wave interference? Two waves can occupy the same place by overlapping when they meet. Interference is the interaction between waves that meet. Interference can be constructive or destructive.

Constructive Interference When waves combine to form a wave with a larger amplitude, it is called constructive interference. Interactions of Waves

Destructive Interference When two waves combine to form a wave with a smaller amplitude than either original wave had is called destructive interference. Interactions of Waves

How do standing waves form? If the incoming wave and reflected wave have just the right frequency, they combine to form a wave that appears to stand still. This is a standing wave: it appears to stand in one place, even though it is two waves interfering as they pass through each other.

Node: destructive interference produces points with zero amplitude. Antinode: points of maximum amplitude on a standing wave

Most objects have at least one natural frequency of vibration. Standing waves occur in an abject when it vibrates at a natural frequency. Resonance is an increase in the amplitude of a vibration that occurs when external vibrations match an object’s natural frequency.

Wave Interactions Making standing waves Singing plates - Standing Waves on Chladni platesSinging plates - Standing Waves on Chladni plates

What is sound? Sound is a disturbance that travels through a medium as a longitudinal wave. Sound waves begin with a vibration that disturbs particles. Sound waves carry energy through a medium without moving the particles of the medium along, each particle vibrates as the disturbance passes.

A common medium for sound is air, but sound can travel through solids. Sound waves do not travel in a straight line. They can diffract, or bend, around openings then spread out so that we can hear them even if the source isn’t close by. What is Sound?

What factors affect the speed of sound? Sound travels more slowly at lower temperatures than at higher temperatures because at lower temperatures it is more difficult for the particles to move and return to their original positions.

The speed of sound depends on the stiffness of the material. Sound travels more quickly in stiff media because when the particles of the medium are compresses, they quickly spread out again. Sound also travels better over long distances in stiff media because sound waves lose energy more slowly than in less stiff media. Sound travels faster in solids and slowest in gases.

In materials of the same stiffness, sound travels more slowly in the denser material. So some metals will allow sound to travel faster than others, such as steel which is less dense than lead. Science - Transmission of Sound

How Do You Hear Where A Sound Is Coming From? - Mr. Wizard's Quick QuizHow Do You Hear Where A Sound Is Coming From? - Mr. Wizard's Quick Quiz Bill Nye The Science Guy S01E12 SoundBill Nye The Science Guy S01E12 Sound

Doppler Effect, Big Bang Theory Style Example of Doppler Shift using car hornExample of Doppler Shift using car horn