Did you know you could cool yourself to -273 °C and be 0K?

Simple Harmonic Motion The oscillatory- or back and forth- motion of a pendulum. Can be represented by a sin curve Waves follow the same pattern

Wave Descriptions The high points on a wave are called crests. The low points on a wave are called troughs. The term amplitude refers to the distance from the midpoint to the crest (or trough) of the wave. Wavelength is the distance between the crests (or troughs) of a wave

Frequency The number of vibrations an object makes per unit of time Can be either the frequency of the vibrating source causing the wave or of the wave itself Example: The number of times a crest passes you in 5 seconds.

Frequency is measured in Hertz (Hz) Represents the number of cycles per second. If one wave passed a given point every second, it would have a frequency of 1 Hz Radio waves are measured to have a frequency of 960 kHz, which is relatively low

If we know the frequency, we can calculate the period, or vice versa Suppose, for example, that a pendulum makes two vibrations in one second. Its frequency is 2 Hz. The time needed to complete one vibration—that is, the period of vibration—is 1/2 second.

The energy transferred by a wave from a vibrating source to a receiver is carried by a disturbance in a medium. It is important to note that the disturbance is what is moving and not the medium itself

Wave speed Wave speed depends on the medium that the wave is traveling through However, no matter what the wave is traveling through, the wavelength, frequency and speed are related through the equation: v = f where v is wave speed,  is wavelength, and f is wave frequency.

Wavelength and frequency vary inversely to produce the same wave speed for all sounds.

If a water wave vibrates up and down two times each second and the distance between wave crests is 1.5 m, what is the frequency of the wave? What is its wavelength? What is its speed?

What is the wavelength of a 340-Hz sound wave when the speed of sound in air is 340 m/s?

Types of waves

Transverse The motion of the particles being displaced is perpendicular to the wave motion

Longitudinal The motion of the particles is parallel to the motion of the waves.

Interference Occurs when waves from different sources meet at the same point at the same time An interference pattern is a regular arrangement of places where wave effects are increased, decreased, or neutralized.

In constructive interference, the crest of one wave overlaps the crest of another and their individual effects add together. The result is a wave of increased amplitude, called reinforcement.

In destructive interference, the crest of one wave overlaps the trough of another and their individual effects are reduced. The high part of one wave fills in the low part of another, called cancellation

https://www.youtube.com/watch?v=wYoxOJDrZzw A standing wave is a wave that appears to stay in one place—it does not seem to move through the medium. Nodes are the stationary points on a standing wave. Hold your fingers on either side of the rope at a node, and the rope will not touch them. The positions on a standing wave with the largest amplitudes are known as antinodes. Antinodes occur halfway between nodes.

A compression travels along the spring similar to the way a sound wave travels in air.

When you quickly open a door, you can imagine the door pushing the molecules next to it into their neighbors. Neighboring molecules then push into their neighbors, and so on, like a compression wave moving along a spring. A pulse of compressed air moves from the door to the curtain, pushing the curtain out the window. This pulse of compressed air is called a compression. When you quickly close the door, the door pushes neighboring air molecules out of the room. This produces an area of low pressure next to the door. Nearby molecules move in, leaving a zone of lower pressure behind them. Molecules then move into these regions, resulting in a low-pressure pulse moving from the door to the curtain. This pulse of low-pressure air is called a rarefaction.

On a much smaller but more rapid scale, this is what happens when a tuning fork is struck or when a speaker produces music. The vibrations of the tuning fork and the waves it produces are considerably higher in frequency and lower in amplitude than in the case of the swinging door. You don’t notice the effect of sound waves on the curtain, but you are well aware of them when they meet your sensitive eardrums.

26.2 Sound in Air Consider sound waves in a tube. When the prong of a tuning fork next to the tube moves toward the tube, a compression enters the tube. When the prong swings away, in the opposite direction, a rarefaction follows the compression. As the source vibrates, a series of compressions and rarefactions is produced.

The speed of sound differs in different materials. In general, sound is transmitted faster in liquids than in gases, and still faster in solids.

Sound cannot travel in a vacuum. 26.3 Media That Transmit Sound Sound cannot travel in a vacuum.

26.4 Speed of Sound The speed of sound in dry air at 0°C is about 331 meters per second, or about 1200 kilometers per hour. This is about one-millionth the speed of light. Increased temperatures increase this speed slightly—faster-moving molecules bump into each other more often. For each degree increase in air temperature above 0°C, the speed of sound in air increases by about 0.60 m/s. V= 331m/s + 0.6m/s/C * T

The Doppler Effect As a wave source approaches, an observer encounters waves with a higher frequency. As the wave source moves away, an observer encounters waves with a lower frequency.

No Doppler effect

Doppler effect

Observer Moving: Source Moving: Towards source: add vo Away from source: Subtract vo Source Moving: Towards observer: subtract vs Away from observer: add vs