waves Flashcards
what do waves transfer
energy
what do mechanical waves travel through
a medium (matter)
whatre all waves categorised into
transverse or longitudinal
describe an give an example for transferse waves
they osciate perpendiculat to the direction of energy transfer. electromagnetic waves
describe and give an example of longitudinal waves
they osscilate parallel to the direction of energy transfer, sound and water waves
whats the equation to calculate wave speed
wavespeed=frequency x wavelength
whatre compressions and rarefactions
in longitudinal waves
-compression is when the waves are close together
-rarefaction is when theyre spread lut
what happens to waves at a boundary between 2 different matierials
theyre either
-reflected
-transmitted
-absorbed
whats refraction
when waves change direction as they cross from 1 medium to another due to a change in velocity
incident ray and incident angle =..
reflected ray and reflected angle
whatre the 5 different ways to descrube wave motion
-frequency in Hz
-wavelentj
-period (1/f)
-amplitude
-wavefront
whatre electromegnetic waves
transferve waves that tranfer energy from the source of thw wave to an absorber
whats the wavespeed of all transferve waves
300 million m/s
name all the waves in the electromegnetic spectrum
RAW MEAT IS VERY UNSANITARY EXCEPT GIRRAFES
-radio waves
-microwaves
-visible light
-ultraviolet
-xrays
-gamma rays
what happens as you go across the spectrum
-wavelength decreases ans frequency increases
whats meant by diffraction
the spreading out of waves as they apass through a gap or obsticle
what happens to diffraction when the gap is narrow
the waves spread further away from the gap
how do we see different visible light
its detected by our eyes in terms of wavelength
all objects —- and —– infrared radiation
emmit and absorb
what does the frequency and amount of emitted radiation depend on
the temp and surface of a given object
-hotter -> more radiaton emitted
what 4 waves are used for communication
-microwaves
-radiowaves
-infrared
-visible light
whats an optical fiber
thin and transparent fibers that transfer signals by either visible light or infrared radiation
why are shorter radiowaves more useful in communications
because they can carry more info without a weakend signal and theyre more easily absorbed
whatre the uses of radiowaves
-tv systems
-radio systems
-bluetooth
whatre the uses of microwaevs
- mobile phones
-satalites
-microwave ovens (when waves are absorbed by water molecules)
whatre the uses of infrared rays
- tv remote controls
-night vision devices
-heating
whatre the uses of visible light
-optic fiber communications, photography
whatre ultraviolet rays used for and whyre they harmful
- security marking and sun beds
-can cause skin cancer and blindness
whatre the issues with x rays gamma rays
are ionising
-x rays can kill cells and gamma rays can cause genetic mutations
whatre the properties of x rays
-affect photographic films in the same ways as light
-absorbed by metal and bones (dense)
-stopped by lead
-transmitted by healthy tissues
whatre the adv and disadvantages of ct scans
- adv: produce detailed 3d images differentiate between soft and hard tissue
dis- expensive and give higher radiation doses
whatre the uses of gamma rays and what are the effects of large doses
- used to steralise medical equipment , kill harmful bacteria in food and kill cancer cells
-can cause genetic mutations in large dosages
what type of waves are sound waves
longitudinal waves that travel through a medium
whats the frequency range of the human ear
20hz to 20,000 hz
how are echos created
by soundwaves being reflected by a smooth and hard surface
how are sound waves defracted
when they pass through a gap (ex-door)
what happens when the frequency of a sound wave increses
the pitch increases
what happens when the amplitude of a sound wave increases
the sound becomes louder
whys ultrasound scans (prenatal) safer than xrays
theyre nonionising and usually reflected
whatre ultrasound waves
sound energy with a frequency above human hearing (over 20,000 hz)
how can u calculate the distance between different mediums
distance = wavespeed x time
whatre the uses of ultrasound waves
ultrasound scans in medicine (prenatal scans)
destroying kidney stones
whats a plane mirror
a perfectly flat mirror
whats the law of reflection
in a plane mirror, angle of incidence is equal to the angle of reflection
whatre angles of incidence,reflection and refraction always measured between
the ray and the normal
whatre the features of.a virtual image
virtual and upsright,cant be projected onto a screen
why can real images be shown on a screen
because all the different light rays are fo used directly onto the screen
whats meant by the refraction of light
the change in direction of light rays when traveling across a boundary from 1 medium to another
what happens when light rays travel from air to glass
the incident ray anglr is greater than the reflected ray angle and light rays bend towards the normal
what happens when light rays travel from glass to air (less dense medium)
reflected angle is greater than the incident angle and the light ray is reflected away from the normal
whats the 1 case wwhere the velocity of wave doesnt change when entering a difff medium
if it enters at 90 degrees (along the normal)
what happens when light is refracted by a prism
a dispersion of light waves and the formation of a spectrum
whats the refractive index
in terms of wavspeed, speed of light in vaccum/speed of light in medium
what does the refractive index measure
how much a medium can reflect a light ray
whats the law of reflection
n(refractive index) = sin i(incident angke)/sin r (refracted angle)
whats the relationship between the refractive index and the critical angle
n= 1/sinc
whats total internal reflection and when can it occur
in a dense to less dense medium.
if angle of incidence is greater than the critical angle.
what type of images do convex lenses produce
real image (lines meet)
how do you describe an image
- upright or inverted
-real or virtual
-magnified or dimminished
what type of image does concave lenses form
virtual
how do you calculate magnification size
image height/object hieght
whats the job of the retina
to focus images
whats the job of the cillary muscles
they alter thickness of an eye lens and are attached by the suspensory ligaments
what 2 strcutures refract light entering the cornea
cornea and lens
whats the near point of the human eye
25 cm
what lenses are used to correct short signtedness
concave (diverging)
whar lenses are used to correct long signtedness
convex (converging lenses)
how are lases used
in eye surgery to correct visual defects
whats the equivilant of film in cameras
the retina in the eye
