waves, electromagnetic waves, light, and sound. waves is a disturbance moves through a medium from...
TRANSCRIPT
Waves, Electromagnetic Waves, Light, and Sound
Waves
• is a disturbance
• moves through a medium from one location to another location
• A medium is a substance or material which carries the wave.
General Wave Properties
• All waves are traveling disturbances.
• All waves transfer energy from place to place.
Parts of a wave
• Crest and Trough
-The section of the wave that rises above the undisturbed position - crest
-That section which lies below the undisturbed position - the trough
Amplitude
• position of the medium to the top of a crest or trough.
• Height of the wave
positive and negative amplitudes
Different amplitudes
Wavelength
*crest to next crest, trough to next trough,* from the start of a wave cycle to the next starting point*Wave to wave
Ex: for wave length
Types of Waves There are three types of waves:
-Mechanical waves.
-Electromagnetic waves
-Matter waves
Mechanical waves
• require a material medium to travel (air, water, ropes).
• These waves are divided into three different types. – Transverse waves– Longitudinal waves – Surface waves
Transverse Waves
• is perpendicular to the direction of wave propagation
• Ex: light, heat, & water waves.
Longitudinal Waves
• is parallel to the direction of wave propagation
Compression and Rarefaction
Compression• Wave that has no crests or troughs• Region where the medium become crowded or
dense• Compress – close together.• Sound waves & shock waves
Rarefaction• The less dense region
Water Waves • involve a combination of both longitudinal and
transverse motions • particle indeed travels in a clockwise circle as
the wave passes.
Electromagnetic waves
• do not require a medium to travel (light, radio
Matter waves
• are produced by electrons and particles.
Pulse and traveling or periodic wave
• a single vibration is produced is a pulse.
• moving regularly up and down, is a traveling or periodic wave .
Measuring Waves
• The number of vibrations per second is called frequency
• Speed of the wave=Frequency X Wavelength
• is measured in hertz (Hz).
The Wave Formula• Velocity = Wavelength x Frequency .
.
• V = x f
• Velocity(m/s), Wavelength (m),
Frequency (hz)
The Nature of Sound
• Sound is caused by vibrations
• Sound waves are Compression waves
• Cannot travel through a vacuum – no particles to push around– Travels faster through liquids and solids than
gases…why?– Travels faster through warmer than cooler
substances…why?
Properties of Sound
• Key Sound Terms– Frequency: How many wavelengths pass a
point each second; hertz (Hz); high frequency=high pitch; humans 20-20,000 Hz
• Pitch: How high or low a sound seems to be
– Intensity: Amount of energy that flows through a certain area in a specific amount of time
• Loudness: Human perception of intensity
• the symbol f is frequency • the symbol T is used for period,• these equations are also expressed as:
Differences in Frequencies
Wave speed
Light wave- faster than soundEx: flying ball reaches your eyes before the
sound wave created by the bat and ball Depends on the medium• Ex: sound waves travel faster in liquids than
solid• Ex: Light waves travel slower in liquids and
solids
Calculating the wave speed
• Speed = Wavelength * Frequency• Speed-v, Frequency-F
• And Wave length -
The Nature of a Sound Wave
*Sound is a mechanical wave*Sound is a Pressure Wave*results from the longitudinal motion of the particles of the medium
Compression and rarefaction
• -As the compression (high pressure) • -rarefaction (low pressure)
Sound
• Measuring intensity of Sound– Intensity is the amount of energy in the wave– Unit of intensity is the decibel (dB)– Above 120 dB cause pain and hearing loss
• Doppler effect– The change in pitch or wave frequency due to a
moving wave source– Examples– Either the source or the observer can be moving
Doppler effect
• Doppler effect can be observed for any type of wave
• Ex: water wave, sound wave, light wave, etc
• the pitch of the siren sound was high; after the car passed by, the pitch of the siren sound was low. That was the Doppler effect
eardrum into vibration motion.
Sound/Music • Noise vs. Music
– Noise—random patterns and pitches– Music—sounds deliberately used in a regular pattern
• Musical Instruments– String vibrations of strings working with a resonator
that amplifies the sound– Brass and woodwinds vibration of air in column
working with a resonator; holes and valves or changing the length of the air column
– Percussion vibration of the membrane causes air inside to vibrate
Sound
• Ultrasound– Medicine high frequency sound waves to
detect and monitor such things as pregnancy, heart disease, and cancer;
– can be used to break up kidney stones and gall stones
Radio Communication
• Radio transmission– Each station is assigned a unique frequency
(called a carrier wave)– FM (frequency modulation); AM (amplitude
modulation); higher frequencies than AM– Article page 405
Behavior of Waves• Types of Interference
– Occurs when two waves combine into one– Constructive: the wave gets bigger
because the crest and trough overlap– Destructive: the wave gets smaller
because a crest and a trough overlaps
Properties of Sound
Intensity:Is the amount of energy that flows through a certain area in a specific amount of time.High intensity carries high energy
Loudness:Is the human perception of the intensity.The intensity of the sound increases, the loudness of the sound you hear increases.
Ultrasonic wave
• Humans can’t hear sound frequencies above 20,000 Hz, called ultrasonic waves.
• Used in medical diagnosis and treatment.
Infrasonic waves
• Is also called subsonic wave
• Have frequencies below 20 Hz
• Too low to hear
• May feel them as a rumble inside your body
• Resonance:
• is the ability of the medium to vibrate by absorbing energy at its own natural frequency.
• Resonance helps amplify the sound created in many musical instrument
• Music:
• Is made of sounds that are deliberately used in a regular pattern.
• Musical instruments contain strings , membranes or columns of air- something that vibrates at its natural frequency to create a pitch.
• Natural frequency depends on the string’s thickness and length and how tightly it is stretched