Module 2 Waves

9-1 – The Nature of Waves • Waves Defined • Wave – • Ex: • Waves and Energy • Waves transfer energy, not matter

9-1 – The Nature of Waves A medium is a substance or material which carries the wave. Electromagnetic Waves are the exception, they do not need a medium to travel.

9-1 – The Nature of Waves • Mechanical Waves • Transverse Waves • Ex: • Longitudinal Waves

9-2 – Wave Properties • Parts of a Wave

9-2 – Wave Properties • Wavelength • Wavelength –

9-2 – Wave Properties • Wavelength and Frequency • Inverse relationship

9-2 – Wave Properties Calculating Frequency Frequency (Hz) = # of waves time (s) Calculating Wavelength Wavelength= 1/ frequency

9-2 – Wave Properties Calculating Frequency Calculate the frequency of this wave if it occurs over 2.5 seconds. Calculate the frequency of this wave if it occurs over 2.5 seconds. Calculate the frequency of this wave if it occurs over 2.5 seconds.

9-2 – Wave Properties Calculating Frequency A ruby-throated hummingbird beats its wings at a rate of about 70 wing beats per second.What is the frequency in Hertz of the sound wave?

9-2 – Wave Properties Calculating Frequency Joe counts waves as they pass a lighthouse. If he counts 15 waves occurring over 4.1 seconds, what is the frequency of the waves?

9-2 – Wave Properties Calculating Frequency A buoy bobs up and down in the ocean. The waves have a wavelength of 2.5 m, and they pass the buoy at a speed of 4.0 m/s. What is the frequency of the waves?

9-2 – Wave Properties Calculating Speed V = f Velocity (m/s) = frequency (Hz) x wavelength (m)

9-2 – Wave Properties Calculating Speed A wave traveling in the water has a frequency of 250 Hz and a wavelength of 6.0 m. What is the speed of the wave?

9-2 – Wave Properties Calculating Speed The lowest pitch that the average human can hear has a frequency of 20.0 Hz. If sound with this frequency travels through air with a speed of 331 m/s, what is its wavelength?

9-2 – Wave Properties Calculating Speed A ship anchored at sea is rocked by waves that have crests 14 m apart. The waves travel at 7.0 m/s. How often do the wave crests reach the ship?

9-2 – Wave Properties Ocean Waves are a transverse and longitudinal wave in one Acts as both:

9-2 – Wave Properties • Amplitude • Amplitude – • Tells about the energy of a wave

Ch 10 - Sound • What causes sound? • Vibrations,Create longitudinal waves • Energy from wave transferred to your eardrum • Your brain interprets this as sound

Ch 10 - Sound • Frequency of sound wave determines pitch (high, low)

Ch 10 - Sound • Instruments create different pitches in different ways • Change length of instrument’s tube by opening holes (wind instruments) • Change length of vibrating string (guitar, violin)

Ch 10 - Sound • Speakers turn electrical energy into sound waves • Vibrating cone inside speaker produce sound waves

Ch 10 - Sound • Radio waves are used in radios. • AM radio waves are measured in kilohertz (kHz) • FM radio waves are measured in megahertz (MHz) • Cell phones operate in gigahertz (GHz)

Ch 10 - Sound • We cannot hear sound in outer space. • Sound waves need particles in a solid, liquid, or gas to vibrate • No air in outer space for sound waves to vibrate.

Ch 10 - Sound • Speed of Sound depends on • Wind conditions • Temperature • Humidity • How fast does sound travel? • 330 meters per second (dry air, 00C) • Faster in liquids (4x faster) • Even faster in solids (15x faster)

Ch 10 - Sound • Frequency and pitch have a direct relationship • Amplitude and loudness have a direct relationship

Ch 10 - Sound • The Doppler Effect • Perceived change in wavelength, frequency, and pitch due to a moving object • No actual change in sound, just perceived change due to the object moving toward you, then away from you.

Ch 10 - Sound • Refraction of Sound • Bending of wave due to speeding up or slowing down • Change in Medium

Ch 10 - Sound • Reflection of Sound Waves(Sound waves bouncing) • Waves reflect at the same angle that the wave hits (law of reflection) • Echoes work on this principle. • Theaters and concert halls are designed to reduce echoes.

Ch 10 - Sound • Applications of Reflected Waves • Sonar “sound navigation ranging” • Sonography • Ultrasound • Echolocation

Ch 10 - Sound Sound Waves Electromagnetic Waves Cannot travel in a vacuum Particles compress and relax as the wave travels through Are longitudinal waves that transmit energy Produce vibrations which can be sensed and some heard Can travel in a vacuum Have a dual quality (particles and energy) Are transverse waves that transmit energy Only portion of electromagnetic waves are visible Have crests, troughs, and a resting equillibrium Reflect, refract, and are absorbed

Electromagnetic Spectrum- Visible • Electromagnetic Waves • Are part magnetic field and part electric field • Have properties of both waves and particles • Can travel without a medium • All travel at the same speed (speed of light)

Electromagnetic Spectrum- Visible • Organizes electromagnetic waves according to frequency • Also shows the wavelength of various waves • Remember relationship between frequency and wavelength • We can only see one small portion of the EM spectrum

Electromagnetic Spectrum- Visible

Electromagnetic Spectrum- Visible • Visible Spectrum • Filters allow certain colors to pass, block others

Electromagnetic Spectrum- Visible • Visible Spectrum • We see colors based on those absorbed and those reflected • Red car = Red light reflected • White car = all colors reflected • Black car = all colors absorbed

Electromagnetic Spectrum- Visible • Visible Spectrum • Opaque objects • Reflect the light • Cannot see through opaque items

Electromagnetic Spectrum- Visible • Visible Spectrum • Translucent objects • Reflect some light, transmits some light • Can somewhat see through translucent items

Electromagnetic Spectrum- Visible • Visible Spectrum • Transparent objects • Transmits light • Can see through transparent items

Electromagnetic Spectrum- Non-Visible • Rest of the Electromagnetic Spectrum (excluding visible light)

Electromagnetic Spectrum- Non-Visible • Radio Waves • Lowest-energy, lowest frequency, largest wavelength • Transmit radio, tv, and cellular signals • Sources: electric circuits

Electromagnetic Spectrum- Non-Visible • Microwave Waves • Lower-energy, lower frequency, larger wavelength • Used to heat food, used in radar guns • Sources: special vacuum tubes, like those in microwave ovens

Electromagnetic Spectrum- Non-Visible • Infrared Waves • Low-energy, low frequency, large wavelength • Heat emitted from warm objects, used in special cameras • Sources: anything that gives off heat

Electromagnetic Spectrum- Non-Visible • Ultraviolet (UV) Waves • high-energy, high frequency, small wavelength • Emitted from the sun, very hot objects, like sun lamps • Sources: special vacuum tubes, like those in microwave ovens

Electromagnetic Spectrum- Non-Visible • X-ray Waves • higher-energy, higher frequency, smaller wavelength • Emitted from x-ray machines, used to image people’s bones • Detected through high speed collisions between electrons

Electromagnetic Spectrum- Non-Visible • Gamma Ray Waves • highest-energy, highest frequency, smallest wavelength • Emitted from nuclear reactions • Sources: radioactive substances • Can be detected with a Geiger counter.