Everything there is to know about Some things we’d like you to know about Waves Mr. Carter and Ms. Dignan’s Physics Class

What is a wave? A wave is a motion of disturbance that transfers energy. A wave is a motion of disturbance that transfers energy. Mechanical waves must travel through a medium. Mechanical waves must travel through a medium. Electromagnetic waves do not require a medium to travel through. Electromagnetic waves do not require a medium to travel through.

v=Rbuhdo0AZDU v=Rbuhdo0AZDU Transverse waves occur when particles move perpendicular to the wave motion Transverse waves occur when particles move perpendicular to the wave motion Longitudinal waves occur when particles vibrate parallel to the wave motion. Longitudinal waves occur when particles vibrate parallel to the wave motion.

Pulse wave – a single disturbance in the medium. Pulse wave – a single disturbance in the medium. Periodic wave –a series of evenly timed disturbances in the medium. Periodic wave –a series of evenly timed disturbances in the medium.

Anatomy of a wave

How we measure waves: Speed (C or v) – How many meters per second is it traveling? Speed (C or v) – How many meters per second is it traveling? Wavelength (λ) – How many meters long is a single wave? Wavelength (λ) – How many meters long is a single wave? Frequency (f) – How many wavelengths occur each second? measured in Hz Frequency (f) – How many wavelengths occur each second? measured in Hz Period (T) – How many seconds does a single wavelength take? Period (T) – How many seconds does a single wavelength take? v = λ/T = fλ v = λ/T = fλ

Sound Basics Sound is an example of a mechanical wave – it requires a medium to travel through. Sound is an example of a mechanical wave – it requires a medium to travel through. Sound waves are longitudinal. Sound waves are longitudinal. com/watch?v=JVhYuq r03IQ com/watch?v=JVhYuq r03IQ com/watch?v=JVhYuq r03IQ com/watch?v=JVhYuq r03IQ

Characteristics of Sound Waves Pitch – the frequency of an audible sound wave Pitch – the frequency of an audible sound wave Infrasonic – f<20Hz Infrasonic – f<20Hz Ultrasonic – f>20,000Hz Ultrasonic – f>20,000Hz The speed of sound depends on the medium that it’s traveling through The speed of sound depends on the medium that it’s traveling through Speed of sound in water v = 1490m/s Speed of sound in water v = 1490m/s Speed of sound in seawater v = 1530m/s Speed of sound in seawater v = 1530m/s

More characteristics of sound waves Intensity – the power with which sound energy travels Intensity – the power with which sound energy travels Intensity = P/area Intensity = P/area Intenisity = P/4πr 2 Intenisity = P/4πr 2 Relative intensity - sound wave intensity as it relates to the threshold of hearing, measured in decibels (dB) Relative intensity - sound wave intensity as it relates to the threshold of hearing, measured in decibels (dB)

Resonance Resonance – the tendency of a system to vibrate with greater amplitude at some frequencies than others. Resonance – the tendency of a system to vibrate with greater amplitude at some frequencies than others. om/watch?v=17tqXgv CN0E om/watch?v=17tqXgv CN0E om/watch?v=17tqXgv CN0E om/watch?v=17tqXgv CN0E ffworks.com/ understanding- tacoma-narrows- bridge-video.htm ffworks.com/ understanding- tacoma-narrows- bridge-video.htm ffworks.com/ understanding- tacoma-narrows- bridge-video.htm ffworks.com/ understanding- tacoma-narrows- bridge-video.htm

The Doppler Effect – An observed change in frequency when there is relative motion between the source of waves and the observer. The Doppler Effect – An observed change in frequency when there is relative motion between the source of waves and the observer. com/watch?v=a3RfUL w7aAY com/watch?v=a3RfUL w7aAY com/watch?v=a3RfUL w7aAY com/watch?v=a3RfUL w7aAY

Thunder and lightning com/watch?v=Sp9bK DHRfsM com/watch?v=Sp9bK DHRfsM com/watch?v=Sp9bK DHRfsM com/watch?v=Sp9bK DHRfsM

What is light? Is it a particle? Is it a wave? Is it a particle? Is it a wave? The current model incorporates aspects of both particle and wave theories. The current model incorporates aspects of both particle and wave theories. Electromagnetic wave – a transverse wave composed of oscillating electric and magnetic fields. Electromagnetic wave – a transverse wave composed of oscillating electric and magnetic fields. All electromagnetic All electromagnetic waves move at the waves move at the speed of light: speed of light: c= 3 x 10 8 c= 3 x 10 8

Electromagnetic Spectrum

Frequency Ranges Wavelengths Wavelengths Frequencies (cycles per sec) Frequencies (cycles per sec) 3 x x x x x x x x x x x x10 22

Radio Waves Biggest Wavelength- Biggest Wavelength- Lowest Frequency- Lowest Frequency- Used for transmitting data over long distances. Used for transmitting data over long distances.

Microwaves Big Wavelength- Big Wavelength- Low Frequency- Low Frequency- Have the perfect frequency for converting to thermal energy. Used to heat things up. Have the perfect frequency for converting to thermal energy. Used to heat things up.

Infrared Waves Big Wavelength- Big Wavelength- Low Frequency- Low Frequency- “Heat Radiation” “Heat Radiation” Used in remote controls. Used in remote controls. This light coming from the sun is what mostly heats our planet. This light coming from the sun is what mostly heats our planet.

Visible Light Waves Medium Wavelength- Medium Wavelength- Medium Frequency- Medium Frequency- This is the light we see This is the light we see This light powers all the photosynthesis on earth. And is responsible for feeding all living things. This light powers all the photosynthesis on earth. And is responsible for feeding all living things.

Visible light is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors. R ed O range Y ellow G reen B lue I ndigo V iolet ROY G BIV

Frequency Ranges of Visible Light Red light has a frequency of roughly 4.3 × Hz, and a wavelength of about 7.0 × 10 ­7 m (700nm). Violet light, at the other end of the visible range, has nearly double the frequency—7.5 × Hz—and (since the speed of light is the same in either case) just over half the wavelength— 4.0 × 10 ­7 m (400nm).

It is no coincidence that visible light falls within the range of wavelengths at which the Sun emits most of its electromagnetic energy—our eyes have evolved to take greatest advantage of the available light.

Ultraviolet (UV) Waves Small Wavelength- Small Wavelength- High Frequency- (high energy) High Frequency- (high energy) Can damage skin cells. Can damage skin cells. Can be used to kill bacteria and sterilize objects. Can be used to kill bacteria and sterilize objects.

X-Rays Very Small Wavelength- Very Small Wavelength- Very High Frequency- (high energy) Very High Frequency- (high energy) Can damage cells. Can damage cells. Can penetrate organs, Can penetrate organs, but not bones. but not bones.

Gamma (UV) Waves Smallest Wavelength- Smallest Wavelength- Highest Frequency- (highest energy) Highest Frequency- (highest energy) Extremely powerful and dangerous to humans. Extremely powerful and dangerous to humans. Used to kill cancer cells Used to kill cancer cells (radiation therapy) (radiation therapy)

C = fλ The frequency (f) of a wave is the number of waves to cross a point in 1 second (units are Hertz or /s) The frequency (f) of a wave is the number of waves to cross a point in 1 second (units are Hertz or /s) λ is the wavelength- the distance from crest to crest on a wave λ is the wavelength- the distance from crest to crest on a wave

The product of wavelength and frequency always equals the speed of light. The product of wavelength and frequency always equals the speed of light. C = fλ Why does this make sense? Why does this make sense? c is a constant value= 3.00 x 10 8 m/s

The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed. The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed. When all colors are being reflected we see white light (white isn’t really a color) When all colors are being reflected we see white light (white isn’t really a color)

When all wavelengths of light are being absorbed we see black (black also, isn’t really a color) When all wavelengths of light are being absorbed we see black (black also, isn’t really a color)