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energy
a property that allows physical work to be done
a property a body has that helps it move against a work (kinetic and potential)
heat (thermal energy)
energy that comes from a substance whose molecules and atoms are vibrating faster due to a rise in temperature (a form of kinetic energy)
the amount of vibration that particles have
insulator
a material that does not allow charge or heat to pass through it easily
conduction
the transfer of heat through solids
heat is passed through vibration to neighbouring particles
convection
the transfer of heat through liquids and gasses
heat decreases density → causes them to rise → particles cool down → heated once again
radiation
heat transfer in the form of infrared waves (no particles involved)
electromagnetic waves
can travel through vacuums (e.g. heat from sun → earth)
particle model
Behaviour of solids, liquids and gasses can be explained by representing them as a group of particles
Energy added/taken away from particles affects movement
Arrangement + movement of particles affects properties
wavelength
the distance between any one point on a wave and the same point on the next wave (e.g. from crest to crest)
frequency
a measure of how many full waves pass through a single point in a second
measured in hertz
shorter wavelength = higher frequency (if same speed)
relates to the speed + wavelength
determines the pitch in a sound wave
amplitude
the distance from the middle of the wave (resting point) to the crest or trough
higher amplitudes = more energy
determines the volume/loudness in a sound wave
speed
a measure of how fast the wave is travelling
usually measured in m/s
varies depending on the medium (travels faster in solids)
velocity
refers to both the speed and direction of a wave
medium
a substance that the wave is travelling through
longitudinal waves
the movement of particles is parallel to the motion of wave (e.g. sound and P-waves)
transverse waves
the movement of particles is perpendicular to the motion of wave (e.g. light and water waves)
crest
the top or highest point above the resting point
trough
the bottom or lowest point from the resting point
compression
the region on a longitudinal wave where the particles are very close together
rarefaction
the region on a longitudinal wave where the particles are very spread out
wave equation
v=λf'
speed = frequency x wavelength
loudness
determined by the amplitude of a sound wave (larger amplitude = louder sound)
pitch
determined by frequency and wavelength (higher frequency, shorter wavelength = higher pitch)
electromagnetic spectrum
consists of a range of invisible waves
all EM waves travel at the speed of light (in order of decreasing wavelength)
radio waves
microwaves
infrared waves
visible light
ultraviolet light
x-rays
γ-rays/gamma rays
reflection
light bounces off an object (e.g. telescopes)
refraction
the bending of light as it passes from one medium to another due to change in speed
faster in less dense matter (e.g. pencil in water)
less dense → more dense: refracted towards the normal
more dense → less dense: refracted away from the noraml
absorption
light is transformed into heat inside an object (e.g. solar cells)
law of reflection
angle of incidence = angle of reflection
normal
an imaginary line that is at an exact 90° from the surface at the point where light strikes
normally represented by a dashed line
wave
“energy carriers”
not made of particles
not all require a medium to travel
light wave
an electromagnetic wave (travels through space at fast speeds)
cannot bend around corners (travels in straight lines)
travels fastest in a vacuum, but slow in other mediums
lens
convex lens
a lens that is curved outwards and is thicker in the middle
causes light rays to converge
can produce either bigger or smaller images
concave lens
a lens that is curved inwards and is thinner in the middle
causes light rays to diverge
produces smaller images
sound wave
longitudinal waves
can only travel through solid, liquid or gas
cannot travel through empty space
produced by all vibrating objects
decibel
a unit used to measure loudness (a normal conversation is about 60 dB)
penetrating power
the ability of each type of radiation to pass through matter
joule
J: a measurement for energy
the amount of work done when a force of 1N is moved through 1m (1kJ=1000J and 1 calorie=4.2J)
radio waves uses
communication (e.g. television and radio) → transmitted easily through air, do not cause damage to body, can be reflected to change direction
other: mobile phones, walkie-talkies, satellites
microwaves uses
cooking food → frequencies are easily absorbed by food molecules, internal energy increases (heating)
satellite communications → pass easily through atmosphere
infrared waves uses
electrical heaters + cookers → frequencies are absorbed by some chemical bonds, internal energy increases (heating)
infrared cameras → all objects emit infrared light
other: deep tissue therapy, military technology
visible light uses
fibre optic communications → coded pulses of light travel through glass fibres from source to reciever
other: vision, photography
ultraviolet radiation uses
sterilising water/hospital + hairdressing equipment → kills bacteria
good for skin → helps to make vitamin D (but overexposure can also cause skin problems)
ionising radiation (UV, x-rays, γ-rays) uses
UV wavesγ: premature skin ageing, increases risk of skin cancer
γ-rays: damages/kills body cells, cancer treatment, nuclear power plants
x-rays: x-rays, security at airport
ionising radiation
can knock electrons from the shells of atoms, turning them into ions
can lead to mutations in cells → cancer (e.g. UV waves, x-rays, γ-rays)
a form of energy/nuclear radiation that acts by removing electrons from atoms/molecules
atoms lose electrons
charge changes (more positive)
becomes ions
radio waves
largest wavelength of EM spectrum (up to 1km long)
lowest energy of EM spectrum (cannot pass through thick material)
microwaves
second lowest energy of EM spectrum
wavelengths tend to be about 1cm long
infrared light
less energy than visible light
wavelength of about 0.01mm
cannot be seen by the naked eye, but can be felt as heat
visible light
only part of the EM spectrum we can see
white light composed of all the colours of the spectrum
violet light: smallest wavelength (400nm), most energy
red light: largest wavelength (700nm), least energy
ultraviolet (UV) light
has lots of energy
shorter wavelengths than visible light (100nm-10nm)
can penetrate skin cells and cause cancer
causes sunburn
x-rays
very energetic
can pass through soft tissue of the human body
very short wavelength (1nm-0.1nm)
cannot pass through bones and teeth (reflected by denser materials)
γ-rays
has the most energy of the EM spectrum
high frequency
shortest wavelength (0.000006nm)
extremely dangerous to humans (can pass through body and cause damage)
α-particle
two protons + two neutrons
high ionisation density
β-particle
electrons
low ionisation density
γ-rays and x-rays
electromagnetic waves
low ionisation density
high penetrating power
conductor
a material that allows charge or heat to pass through it easily
hertz
a measurement for frequency (Hz)
colour
a property of visible light that depends on its frequency
lowest frequency of light that we can see is red, and the highest is purple
transmission
the passing of light through a material
diffraction
the spreading of waves as they pass through or around an obstacle
e.g. a megaphone
scattering
a change in the direction of motion of a particle because of a collision with another particle
the spreading of a stream of particles or a beam of rays, as of light, over a range of directions as a result of collisions with other particles
e.g. the prism experiment
shadow
an absence of light
light blocked by an object
transparent
allowing nearly all light to pass through
e.g. window
translucent
allowing only some light to pass through
object appears blurred
e.g. sunglasses
opaque
not allowing light to pass through
e.g. a rock
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Flashcard (69)