Physics - Waves Flashcards
how to waves transfer energy
causing particles of matter to oscillate
longitudinal waves characteristic
oscillation are parallel to direction of energy transfer
longitudinal waves examples
sound waves
p waves
transverse waves characteristics
oscillations are perpendicular to direction of energy transfer
transverse waves example
electromagnetic waves
(microwaves, light, UV)
what is compression
compressed region
what is rarefaction
stretched region
wavelength
distance between a point on a wave and the closest next point which is exactly identical
represented by lambda
amplitude
maximum distance a particle can be displaced from rest position
frequency
number of waves passing a point per second, measured in Hertz (Hz)
1Hz is equivalent to 1 complete wavelength per second
sound waves that have higher amplitude
louder
sound waves that have higher frequency
higher pitch
wave speed
distance travelled by wave over time
speed equation
frequency (Hz) x wavelength
relationship between frequency and wavelength
inversely proportional
speed of longitudinal waves through different states of matter and why
solid - fastest
liquid - fast
gases - slowest
transfer energy by causing particles to oscillate
sound waves cant travel in a …
vacuum
why can EM waves travel through a vacuum
particles oscillating in an EM are the electrons of the wave itself, which means it does not require additional matter and is able to travel through a vacuum
speed of waves when travelling through matter
- speed depends upon medium/density of medium
- frequency is usually constant
- changes in speed changes wavelength (speed and wavelength are directly proportional)
radiowaves
wavelength
uses
dangers
wavelength = >10cm
uses = communication
dangers = none?
microwaves
wavelength
uses
dangers
wavelength = 10^-2 m
uses = wavelengths that pass through water are used for communication, wavelengths absorbed by water are used for cooking
dangers = must be kept inside of microwave by metal grill or could heat body
infrared
wavelength
uses
dangers
wavelength = 10^-5 m
uses = heat is radiated as infrared - uses for heat cameras, cooking e.g. grilling toasting etc
dangers = responsible for burns and greenhouse effect
visible light
wavelength
uses
dangers
wavelength = 10^-7 m
uses = optical fibres
dangers = eye damage
ultraviolet
wavelength
uses
dangers
wavelength = 10^-8 cm
uses = fluorescent marking (chemicals are used which absorb UV light and emit visible)
dangers = skin cancer, ionising radiation
x ray
wavelength
uses
dangers
wavelength = 10^-10 cm
uses = medical imaging
dangers = ionising radiation
gamma
wavelength
uses
dangers
wavelength = 10^-12
uses = sterilising, cancer, radiotherapy, medical imaging
dangers = ionising radiation
relationship between EM’s energy and EM’s frequency
directly proportional
relationship between EM’s energy and EM’s wavelength
inversely proportional
what speed do EM waves travel at
speed of light
all at the same speed
reflection
occurs when a wave bounces off a surface without being absorbed by it - usually causes the wave to change direction
law of reflection
angle of incidence = angle of reflection
refraction
occurs when a wave enters a medium with a different optic density and change direction due to a change in speed
which line are both angle of incidence and angle of reflection measured relative to
normal
what is the normal
imaginary line at 90 degrees to the surface
what colour is the end of the spectrum which is refracted least when entering prism
red
what colour is the end of the spectrum which is refracted most when entering prism
blue
will sound waves reflect and refract
yes
doppler effect
when there is relative motion between a source of waves and an observer, the wavelength and frequency of the waves received when there is no relative motion
doppler effect when source moves toward observer
frequency increases
wavelength decreases
doppler effect when source moves away from observer
frequency decreases
wavelength increases
what causes greater doppler shift
faster movement
how are sound waves produced
from a vibrating source
causes medium to vibrate and pattern of vibrations travels away from source as sound waves
sound wave : frequency
PITCH
same as frequency as vibration from source
sound wave: amplitude
LOUDNESS
depends in the amplitude of vibrations of the source
sound wave: speed
determined by medium through which they are travelling through and NOT by the source
what happens when sound arrives at detector
sequence of compressions and rarefactions causes pressure at the detector to vary
this exerts a varying force on the detector and this is what is detected
(eardrum moved by this force)
echo
sound heard after sound waves reflect from one or more surfaces
reflection can be used to measure distances
equation
distance =
velocity x time x 1/2
what principle is used by both sonar and ultrasound
distance =
velocity x time x 1/2
principle that dividing by two accounts for the fact that time is measured is time taken for the wave to travel from the emitter/reciever to the object and back again
human hearing range
20Hz –> 20KHz
ultrasound range
> 20KHz
ultrasound
- depth detection
- non invasive medical procedures
- ultrasound can detect a boundary between different tissue types as certain fractions of ultrasound are reflected at each boundary
- create image of soft tissue within body
ultrasound: what does the time taken for the reflected waves to reach detectors correspond to
depth of each boundary
