unit 6 physics

sound waves, ear sound

• sound waves in air fuelled into ear, hit th e eardrum which is a thin membrane

• cause eardrum and other parts o the ear to vibrate, cause sensation of sound

radiowaves

• can be produced by oscillations in electrical circuits

• when radio waves are absorbed, they may create an alternating current, with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical current

sunlight

• mixture of all colours, paper white, white light is normal light

transmit light

• either transparent or translucent, scatter most light and only let some through

opaque object

• colour depend on which wavelength of light are most strongly reflected

reflect, refract, sound waves

• reflected by hard surfaces, echoes

• refracts, enterdenser material, they speed up, frequency same, wavelength different

ripple tank

• transparent shallow tray of water, with a light shining down through it onto. white cad, below in order to clearly see the motion of the ripples creates on the water’s surface

• used to measure and calculate frequency, wavelength, speed of wates

• electrical components near water, shock and damage, secure components before adding water, take care not to splash

concave lens

• always virtual image if placed a screen where the image appears, we wouldn’t see an image on the screen

• right way up, diminished, and on the same side of the lens as the object

• thicker at the edges than the centre, so when rays of light hit, they diverge, spread out

infrared raditation

• when visible light and high frequency infrared radiation are absorbed by earth’s surface, planets internal energy increases and surface gets hotter

• some of this energy is transferred to the atmosphere by cnnventio and conduction

global warming

• ears radiates lower frequency radiation, some is transmitter thorough atmosphere back to space, some absorbed by greenhouse gases in te atmosphere, gg re-emit in all directions, some back to earth, which is reabsorbed

electrical devices

• electrical devices can be made which produced electrical oscillations over a range of freqencies

• these can then easily be converted into mechanical vibrations to produce sound waves beyond the range of human hearing

convex lens

bulges outwards, using rays of light parallel to the axis to be Brough tighter, convert at the principal focus

using convex lens

• magnifying glasses, binoculars, correct long sightedness as it focuses the rays closer

near than 1 FL

• virtual image

• right way up

• magnifedi

• on the same side of tehe lens

more than 2 FL

• diminished

• inverted

• real

Leslie cube

• how absorption depends on surface

• stick ball bearing to the back of 2 different surfaces with wax

waves in a ripple tank experiment

• set up ripple tank with about 5cm depth of water

• adjust the high of the wooden rod, so it just touches the surface of the warer

• switch on lamp and motor, adjust until low freq. waves observed

• measure length of number of waves then divide by number of waves, wavelegth

  • photo of the card with the ruler next to it

• count the number of waves passing a point in 10 seconds, divide by 10 seconds

• speed = frequncy x wavelength

mechanical waves

• cause oscilationsof particles ins solid, liquid, gas and must have a edmqum to travel through

electromagnetic

• cause oscillations in electrical an magnetic fields

rest position

undisturbed position of particles or fields, when they aren’t vibrating

displacement

• distance that a certain point in the medium has moved form its rest position

electromagnetic waves

• transfer energy from the source of the waves to an absorber

all the electromagnetic waves

• radiowaves

• microwaves

• infrared

• visible light

• ultraviolet

• x rays

• gamma rays

• radio wave, low frequency, long wavelength

UV

• damage surface cells

• lead to sunburn

• skin age prematurelt

• eventually can cause blindness

• skin cancer

X- ray

• ionising radition

• mutations of genes

• causing cancer

• loq frequency, most pass through soft tissue

uses of radio waves

• TV and radio

• long wavelength, travel without losing quality

uses of microwaves

• satellites communications, cooking food

• can penetrate atmosphere, to reach satellites

IR waves

• cooking food, infrared cameras

• transfer thermal energy

visible waves uses

• fibre optics

• best reflections, scattering in glasses

UV waves

• sun tanning, energy efficient waves

• radiates the least energy but more energy

x rays

• medical imagery and treatment

• very high energy, and can penetrate material easily

convex lens

• object being magnified must be closer to the lens than the focal length, image virtual, rays don’t actually meet, couldn’t see this on a screen

convex

• different convex lenses have different focal length, depending on the strneght of the lens

black body radiation

• all objects emit EM radiation due to the energy in their thermal energy store

• intensity and wavelength distribution of emission depends on the bodies temperature

• if absorbs more without emitting same amount, temperature will rise until absorption is equal to emission again

seismic

infrasound, frequencies under 20 Hz

at boundary

• transmitted, often leads to refraction

• absorbed, transfer energy to the materials energy stores

• reflected

• infrared light has frequencies which are absorbed by csome chemical bonds, internal energy of the bonds increase when they absorb infrared light, causing heating

optic fibres

• carry data over long distances as pulses of visible light

colour filters

• work by absorbing certain wavelength and transmitting others

• primary only transmit that colour

• secondary, let through both the wavelength of light of that colour, and wavelengths of the primary colours that can be added to make that colour

1-2FL

• magnified

• inverted

• real