Physics, paper2 , waves

what are the two types of waves

transverse and longitudinal

What are transverse waves?

Waves that move at right angles to the direction of the wave (perpendicular)

What are longitudinal waves?

Oscillations are parallel to the direction of energy transfer

How do waves pass energy

particles oscillate about a fixed point passing on the energy to the next particle

4 properties of waves

amplitude, wavelength, frequency, and period

what is the frequency of a wave

number of naves that pass a fixed point per second

What is the amplitude of a wave?

The maximum displacement that any particle achieves from its undisturbed position

What is the wavelength of a wave?

distance from one point on a wave to the equivalent point on the next wave

what is the period of a wave

The time taken for one complete oscillation

what does amplitude indicate

the amount of energy a wave is carrying

how to measure wave speed

count number of waves passing a fixed point per second

what 4 things can happen to waves

reflected, refracted, absorbed, transmitted

what does the direction of refraction depend on

the angle at which the wave hits the boundary
the materials involved

What is the refractive index?

the way in which a meterial affects refraction

when does light move away from the normal

when travelleing from a high refractive index to a low refractive index

what is the cause of refraction

difference in wave speed in different media

what happens when light enters a object which it travels slower at an angle

-first part of the light slows down
-yeh rest of the wave continues
-causes the wave to change direction

what does the loudness of sound relate to

amplitude

What does the pitch of a sound depend on?

frequency and wavelength

what is sound due to

vibrations of particles

what can sound cause in a object

entire objects to vibrate with the same frequency

how do sound waves work in the ear

cause the ear drum and other structures to vibrate which is heard as sound

what frequencies can humans hear?

20Hz to 20kH

what frequenxe are ultrasonic waves

greater than 20kHz

what happens when a ultrasonic wave meets the boundary between to media

it is partially reflected

how can you determine how far away a boundary is

measuring time taken for reflected ultrasonic waves to return to a detector

Uses of ultrasonic waves

-detecting defects in materials
-pre natal scanning
-detection of kidney stones and tumours
-producing images of damaged ligaments

what is echo sounding

use of ultrasonic waves for detecting objects in deep water and measuring depth of water

How does echo sounding work?

sending ultrasound pulse into water which is reflected back when it hits a surface

how does echo sounding calculate the depth of the sea water?

time take for pulse to be sent out and reflection being detected/2

what are 2 types of seismic waves produced in a earthquake

-p waves
-s waves

what are p waves

longitudinal waves
-travel at speed of sound
-travel at diff ent speeds in solids and liquids

what are s waves

transverse waves
-not able to travel through liquids

What are faster P or S waves?

P waves

what happens during an earth quake

-seismic waves travel out from the earthquake through earth
-seismic waves travel a curved path through earth
-detectors are placed to detect where waves arrive

why do waves travel i. a curve through the earth

increased density with depth

what are s the s wave shadow zone

-s waves can't travel through liquid in the outer core
-large shadow zone on the opposite side of earth
-shadow zone provides evidence about the size of the core

What is the P-wave shadow zone?

-they are refracted at boundary between semi-solid mantle and liquid outer core
-refracted again at boundary between liquid outer core and solid inner core
-determines the composition of inner and outer core

what type of waves are electro magnetic waves

transverse waves

features of electro magnetic waves

-spectrum containing difference frequency
-the wavelength of the wave affects how it's absorbed, transmitted, reflected or refracted

uses for radio waves

tv radio bluetooth

radio waves explanation

low energy waves- not harmful

microwaves uses

Cooking and satellite transmissions

explanations for microwaves

-travel in straight lines through the atmosphere
-ideal for transmitting signals to satellites and back down to recievers

uses for infrared waves

heaters, cooking, infrared cameras

i fared waves explanation

-electric grills glow red as electric flows through them
-transmits i fared energy which is converted back to thermal energy

uses for visible light

fibre optic communications

visible light explanation

-light travels down optical fibres from one end to the other without being lost through the sides

ultraviolet waves uses

Energy efficient light bulbs, security marking, sunbeds

ultraviolet waves explanation

-in bulbs uv waves are produced by the gas in the bulb when excited by electric current
-uv waves ten absorbed by coating on the bulb which fluoresces to give off light

uses for x rays

medical imaging, treatments

x rays explanations

-penetrate soft tissue but not bone- display shadows where bones are

gamma rays uses

sterilising food, tumour treatment

gamma rays explanation

most energetic of all em waves can destroy bacteria and tissues

what are radio waves caused by

Oscillations in electrical circuits

what does frequency of radio wave rely on

frequency matches frequency of electrical oscillation

what happens when radio waves are absorbed by conductor

create an alternating current with same frequency as radio wave which is how the signal is recieved

how can changes in atoms create hazards

-can cause em waves to be generated over a higher frequency waves

what causes x rays, uv waves, visible light and infrared waves be produced

electrons moving between energy levels due to heat or electrical excitation

what can changes in the nucleus of an atom cause

generate waves- unstable nucleus can give out excess energy as gamma rays

why are uv, x and gamma rays hazardous

-uv- cause skin to age and increase risk of skin cancer
-x and gamma- ionising radiation - damage cells can cause gene mutations and cancer

two types of lenses

concave on convex

convex lense

-wider in middle
-parallel rays of light brought to focus as principle focus

focal Length

the distance from the center of a lens to the principle focus

concave lens

-wider at edges
-parallel light spread out
-makes rays to appear have come from pf on the same side of lens they originated

what images can convex lenses produce

real or virtual

what to do when drawing ray diagrams

-draw principle exist-line that runs through lens
-use correct lens symbol

specular reflection

reflection from a smooth surface in a single direction

diffuse reflection

reflection from a rough surface where the light is scattered

what does each colour have

it's own narrow band of wavelength and frequency

what happens when a opaque object appears coloured

-it's reflecting light of that particular wavelength
-it is absorbing other wavelengths

how do filters work

absorbing some wavelengths and not others

what does the rate at which an object emits radiation depend on

nature of the surface and it's temperature

what would a perfect black body do

-absorb all infrared radiation
-does not reflect or transimit any radiation

what does the temperature of an object depend on

-rate at which it emits radiation
-wavelength of radiation it emits
-balance between emmision and absorption

what is a black body

a perfect emitter and absorber

what happens in a black body as the temperature increases

amount of overall radiation the body emits decreases
-intensity of shorter wavelengths increases faster

why does the ground on a sunny day heat up

-absorbs suns radiation faster than it emmitt
-eventually they will equal out a reach a constant temp

what does the temp of the earth depend on

-how much energy it recieves from the sun
-how much energy is reflected back to space
-how much energy it emits to space