amplitude of a wave
this is "how high" the wave is from its undisturbed position, it is not crest to trough.
diffuse reflection
light is incident on a rough surface, parallel rays of light are reflected at random angles, image cannot be formed
electromagnetic waves
transverse waves that transfer energy, the electric and magnetic fields that make up an em wave oscillate perpendicular to the direction in which the wave is travelling, they form a continuous spectrum, can travel through a vacuum at the same speed
focal length
distance between the principal focus and the centre of the lens
frequency of a wave
the number of waves passing a certain point each second
gamma rays and their uses
produced when there are changes to the nuclei of atoms, they can both penetrate body tissue e.g. technetium 99m is injected into the patient's bloodstream and the gamma rays which it emits in the kidneys pass out of the body and can be detected which provides imformation to doctors on the patient's condition. can also be used to damage body tissue e.g. in radiotherapy - gamma rays emitted by iodine-131 which is swallowed by the patient can be used to treat a thyroid condition
how do we hear sound
the sound wave sets our ear drum into oscillation, this causes the small bones in the ear to oscillate, as a result an electrical signal which is produced in the cochlea is sent to the brain via the auditory nerve
image of an object formed in a plane mirror (flat surface)
virtual image, upright, appears to be the same distance behind the mirror as the object is in front of it
image of an object from a concave (diverging) lens
virtual, upright, diminished
image of object between 2f and f from a convex (converging) lens
real, inverted, magnified
image of object between f and a convex (converging) lens
virtual, upright, magnified
image of object further than 2f from a convex (converging) lens
real, inverted, diminished
law of reflection
the angle of incidence is equal to the angle of reflection
longitudinal wave e.g. sound waves, P-waves
vibrations/ oscillations are parallel to the direction of energy transfer
P-waves (primary waves)
longitudinal waves, can travel through both solid and liquid rock (travel quicker in solid rock)
perfect black body
absorbs all of the radiation that is incident onto it and doesn't reflect or transmit any of it, perfect emitter of radiation
period of a wave
the time taken for one complete wave to pass a certain point
principal focus of a convex (converging) lens
point through which light rays that are initially travelling parallel to the principal axis will travel after being refracted by the lens
refraction
the change in direction of a wave as it travels from one medium into another, it happens when a wave changes speed upon travelling from the first medium into the second
S-waves (secondary waves)
transverse waves, can only travel through solid rock not liquid rock
specular reflection
light is incident on a smooth, polished surface, parallel rays of light are reflected at the same angle, virtual image produced
transverse wave e.g. electromagnetic waves, water waves, S-waves
vibrations/ oscillations are perpendicular to the direction of energy transfer
ultrasound
sound waves with frequencies above 20kHz, each time they arrive at a boundary between one material and another, they will be partially transmitted and partially reflected, the time delay between sending and receiving an ultrasonic pulse allows the depth of a given boundary within the object to be determined
ultraviolet rays and fluorescence
a fluorescent substance can absorb uv radiation and use its energy for the emission of longer-wavelength visible light
uses of infrared radiation
electrical heaters, cookers, remote controls, infrared cameras, some fibre-optic communications
uses of microwaves
cooking food, mobile phone networks, satellite communications (pass easily through earth's atmosphere), short range bluetooth communication
uses of radio waves
radio and television signals, radar
uses of visible light
human sight, lasers, fibre-optic communications
virtual image
an image that cannot be projected onto a screen
wave
transfers energy from one place to another without a permanent motion of the material which it is travelling through
wavelength
this is the distance between two corresponding points on the wave and is measured in metres. the two points can be crest to crest, trough to trough
what happens when a wavefront travels from deep water into shallow water
the frequency of the wave stays the same however the wavelength is shorter is shallow water because the waves travel more slowly, the speed of a wave is directly proportional to its wavelength
x-rays and their uses
produced by the rapid deceleration of free electrons, they pass easily through soft body tissue but are absorbed effectively by bone so are used in medical imaging. can also damage body tissue so are used in medical treatment to control or kill tumours
longitudinal waves
oscillations are parallel to the direction of travel of the wave
sound waves
features of a wave
wave equation