WAVES Flashcards
Waves transfer ______ in the ___________ they are _______
waves transfer energy in the direction they are travelling
what is the amplitude of a wave
is the maximum displacement of a point on the wave from its undisturbed position
what is the wavelength of a wave
is the distance between the same point on two adjacent waves
what is the frequency of the wave
is the number of complete waves passing a certain per second
what is frequency measured in
hertz
what is the equation for the period of a wave
T=1/F
T= PERIOD
F=FREQUENCY
THE TWO TYPES OF WAVES
transverse and longitudinal
in transverse waves….
the oscillations are perpendicular to the direction of energy transfer
examples of transverse waves
all electromagnetic waves
waves in water
a wave on a string
in longitudinal waves
the oscillations are parallel to the direction of energy transfer
examples of longitudinal waves
sound waves
shock waves
equation for wave speed
frequency * wavelength
waves can be….
absorbed, transmitted or reflected
angle of incidence =
angle of reflection
what is specular reflection
specular reflection is when a wave is reflected in a single direction by a smooth surface
what is diffuse reflection
is when a wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions
all EM waves are…
transverse waves
all EM waves travel…
at the same speed through air or a vacuum
WHEN a wave crosses a boundary between materials at an angle
it changes direction
what depends on how much a wave is refracted
how much the wave speeds up or slows down
and density
the higher the density
the slower the wave travels through the material
what is refraction
when waves change direction at a boundary
what happens if a wave crosses a boundary and it slows down
it bends towards the normal
what happens if a wave crosses a boundary and it speeds up
it will bend away from the normal
how can you produce radio waves
using an alternating current in an electrical circuit
what are radio waves used for
are mainly used for communication
radios
tvs
what are microwaves used for
microwaves are used for communication to and from satellites
heating food
what is infrared radiation used for
infrared cameras
increase or monitor temperature
explain why signals between satellites are transmitted as microwaves
because they can pass through the earth atmosphere
what is given out by all hot objects
infrared radiation
uses of visible light
fibre optic cables to transmit data
how do fibre optic cables work
they work because of reflection. the light rays are bounced back and forth until they reach the end of the fibre
uses of UV
UV pens
sun tanning
uses of xrays and gamma rays
they are used in medicine
xrays are used to see if people have broken bones
both used to treat people with cancer
gamma can be used as a medical tracer
how do radiographers use xrays and gamma rays to treat people with cancer
these rays can kill the cancer cells
how is gamma radiation used in a medical tracer
a gamma emitting source is injected into the patient and its progress is followed around the body
gamma radiation is used as can pass out of the body to be detected
how do you get an xray image
xrays pass easily through flesh but not so easily through bone. the amount of radiation absorbed gives you the xray image
what do radiographers wear to protect themselves from radiation
lead aprons
what is the electromagnetic specttrum
radio waves microwaves infrared radiation visible light ultraviolet xrays gammarays
as you go down the electromagnetic spectrum
the wavelength decreases
the frequency increases
what are the ionising ones in the EM spectrum
UV
gamma
xrays
why are low frequency waves less harmful
they don’t transfer much energy and so mostly pass through soft tissue without being absorbed
why are high frequency waves dangerous
they all transfer lots of energy and so can cause lots of damage
why is uv radiation dangerous
damage surface cells which can lead to sunburn
increased risk of skin cancer
why are xrays and gamma rays dangerous
types of ionising radiation
can cause gene mutation or cell destruction
cancer
how do lenses form images
by refracting light and changing its direction
WHAt are the two main types of lens
concave and convex
what is a convex lens
a convex lens bulges outwards it causes rays of light parallel to the axis to be brought together at the principal focus
what is a concave lens
a concave lens caves inwards. It causes parallel rays of light to spread out
what is the principal focus of a convex lens
is where rays hitting the lens parallel to the axis all meet
what is the principal focus of a concave lens
is the point where rays hitting the lens parallel to the axis appear to come from
to describe an image properly what do you need to say
how big it is compared to the object
real or virtual
upright or inverted
how would you draw a ray diagram through a conc=vex lens
draw a ray from the top of the object to the lens
draw a ray from the top of the object through the middle of the lens
the ray that has touched the lens should be refracted through the focal point
the ray that goes through the middle of the lens should be extended
where the rays meet is the image
what should you always remember when you draw rays
arrows on the rays
an object at 2f will produce….
a real, inverted image the same size as the object and it is at 2f
an object between f and 2f will produce…
a real inverted image bigger than the object and beyond 2f
an object nearer than f will produce..
a virtual image the right way up bigger than the object and the same side of the lens
concave lenses always produce a
virtual image
magnification=
image height/object height
