Waves Flashcards
What do waves do
They travel in straight lines
Refract,reflect,diffract
Transfer energy from one place to another without the transfer of matter
…
How many pulses make up a full wave
2
What is a transverse wave
A transverse wave is a moving (progressive) wave that consists of oscillations occurring perpendicular (or right angled) to the direction of energy transfer.
What is a wavefront
Straight line across a wave where all particles are in phase
Wavelength
Distance between 2 corresponding points on 2 successive waves
Frequency
Number of waves complete per seconds
Time period
Time taken for one complete wave
Crest/peak
Highest part of a wave
Trough
Lowest part of a wave
Amplitude
Maximum displacement from the waves undisturbed position
Wave speed
Distance travelled by wavefront per second
Medium
Matter the wave is traveling through
Describe the disturbance of a transverse wave
The disturbance is 90 degrees to the direction of the wave
What is the difference between transverse and longitudinal waves
In a transverse wave, the disturbance is 90 degrees to the wave and they don’t require a medium to travel through
Longitudinal waves require medium and occur 180 degrees/in the same plane as the direction of the wave
Describe the displacement of the medium in longitudinal waves
Parallel to the propagation of the wave
What are the equivalents of peaks and troughs in longitudinal waves
Compressions and rarefactions
When do échos occur
when a wave is directly reflected from a boundary
Refraction
Bending of light when it passes from one medium to another of different optical densities and is caused by the changing of speed in the media
What happens to the wave speed, wave length, direction and frequency when a wave refracts
The wave speed, length and direction changes but frequency will remain the same
How can we minimize refraction
By limiting the angle at which the ray enters the new optical density
What is diffraction
The bending of waves through a gap
How does the size of the gap through which the wave diffracts affect the wavelength
The smaller the sound the larger the wavelength, the greater the wave will spread out through the gap
How does frequency affect the diffraction of a radio wave
High frequency is little diffraction
Low frequency is large diffraction
What are the advantages of digital signals
They carry
What is refractive index
The ratio of the speed of light in a vacuum to the speed of light in a medium
What is total internal reflection
Complete reflection of a light ray reaching a boundary with a less dense medium when the angle of incidence exceeds the critical angle
i>c
What are the uses for total internal reflection
Fibre optic cables-transmit light down fibres
Communication and medical examinations
What are the 3 parts in an optic fibre cable
Coating
Cladding
Core
What is the critical angle
The angle of incidence in the medium of greater optical density that results in an angle of refraction of 90 degrees
What are the 2 main types of lenses
Concave and convex
Diverging and converging
What happens when parallel light rays pass through a convex lense
They converge at one point called the principle focus.
What type of image will be produced when an object is closer to the lens that then focal point
A magnified virtual image
What type of image is formed when an object is further from the lens than the focal point
inverted and real
What does it mean if an image is real
The image can be projected on a screen
What is another word for backtracking lines
Extrapolating
Why does dispersion happen
The refractive index for frequencies of light is slightly different, causing the angle of refraction to vary by a small amount
What is dispersion
The refraction of white light as it passes and then disperses through a prism into 7 colours. The colour with the highest frequency and smallest wave length, violet refracts the most and red the least
Monochromatic
Light of a single frequency
Normal
Line that intersects given line or surface at 90 degrees
What are the primary light colours
RGB
Principal focus point
Point where a beam,parallel to the principal axis appears to converge after passing through the lens
Principal axis
Line passing through the centre of a lens or curved/spherical mirror and parallel to the axis of symmetry
Focal length
Distance between centre of a lens/curved mirror and its focal point
Angle of refraction
Angle which a refracted line/ray makes with a normal line to the surface at the point of refraction
Angle of reflection
Angle which a reflected line/ray makes with a normal line to the surface at the point of reflection
Angle of incidence
Angle which an incident line/ray makes with a normal line to the surface at the point of reflection
What is long sightedness called
Hyperopia
Close=blurry
What is short sightedness called
Myopia
Where does the image form and what lens is used to treat miopia
Before the retina, concave/diverging lens
Where does the image form and what lens is used to treat hyperopia
Behind the retina, convex/converging lenses
How does text appear in a mirror
Laterally inverted
Describe what is meant by wave motion as illustrated by vibrations in ropes and springs, and by experiments using water waves
Wave motion is the transfer of energy from one point to another which can be demonstrated by hanging an object on a stretched string and sending a pulse through the string resulting in it bobbing up and down. When a pebble is dropped into a pond circular ripples move outward on the surface of the water.
What can be modelled as a transverse wave
Electromagnetic radiation (such as light),
water waves
seismic S-waves
What can be modelled as longitudinal waves
Sound waves
Seismic P-waves
Reflection
Change in direction of a wave when it strikes a surface
i=r
Refraction
Change in speed of a wave when the medium changes
Diffraction
Spreading of a wave as it goes through a gap or around a corner
Properties of the electromagnetic spectrum (3)
All transverse
Travel at 3x10*8 in air
Can travel through a vacuum
Electromagnetic spectrum (7) in order of wavelength
Radio waves (greatest )
Microwaves
Infrared rays
Visible light (ROYGIBIV)
Ultraviolet
X-rays
Gamma rays (shortest)
What on the electromagnetic spectrum has the highest frequency and lowest wavelength
Gamma rays
Use of radio waves (3)
Radio and television transmissions
Astronomy
Radio frequency identification (RFID)
Uses of microwaves (3)
Satellite television
Mobile phones
Microwave ovens
Uses of infrared waves (5)
Thermal imaging
Optical fibres
Intruder alarms
Short range communications (remote for TV)
Electric grills
Uses of visible light waves (3)
Vision
Photography
Illumination
Uses of ultraviolet waves (3)
Sterilizing water
Detecting fake bank notes
Security marking
Uses of X-ray waves (2)
Medical scanning (broken bones)
Security cameras (detecting metallic objects in luggage)
Uses of gamma rays (2)
Sterilising food + medical equipment
Detecting + treating cancer
Dangers of microwaves
Internal heating of body-cells
Dangers of infrared waves
Can cause skin damage and burns
Dangers of ultraviolet waves
Can cause damage to surface skin cells and eyes if exposed too long leading to cancer and eye conditions
Dangers of X-ray and gamma rays
Causes mutation/damage cells in the body leading to cancer (they are ionising)
Why/how Communication with artificial satellites uses electromagnetic waves
Done with microwaves
Some satellite phones use low orbit artificial satellites
Some satellite phones and direct broadcast satellite television use geostationary satellites
Systems of communication that rely on electromagnetic waves (4)
Mobile phones
Bluetooth
Optical fibres
Communication with artificial satellites
Application of electromagnetic waves in mobile phones
Wireless internet uses microwaves because they can penetrate some walls + only require a short aerial for transmission + reception
Application of electromagnetic waves in Bluetooth
Radio waves as they pass through walls
Application of electromagnetic waves in optical fibres
Visible light/infrared is used for cable television + high speed broadband connections because glass is transparent to visible light and some infrared and visible light and short wavelength infrared can carry high rates of data
Speed of sound in air
330-350 m/s
Range of frequencies audible to humans
20 - 20 000 Hz
Ultrasound
Sound with a frequency higher than 20 000 Hz
Types of signals that can transmit sound
Analogue
Digital
Advantages of digital over analogue signals
Increased rate of transmission
Increased range of transmission (easier to regenerate)
Analogue signals
Continuous in value
Digital signals
Discrete (fixed) in values
Describe the production of sound by vibrating
sources
When an object vibrates, it causes movement in surrounding air molecules. These molecules bump into the molecules close to them, causing them to vibrate as well.
Describe the longitudinal nature of sound waves
all the particles of the medium (such as gas, liquid or solid) vibrate in the same direction as the wave
Behaviour of waves (3)
reflection at a plane surface
refraction due to a change of speed
diffraction through a narrow gap
Describe the formation of an optical image by a plane mirror (3)
Virtual
Upright
Same distance from mirror
What are ripple tanks often used to show (4)
Reflection at a plane surface
Refraction due to a change in speed caused by a change in depth
Diffraction due to a gap
Diffraction due to an edge
Principal focus/focal point
the point where rays of light travelling parallel to the principal axis intersect the principal axis and converge
Use of a single lens
Magnifying glass when the object is just beyond the principal focus of the lens
Uses of total internal reflection (2)
Optical fibres (communications, endoscopes, decorative lamps)
Prisms ( binoculars, telescopes, cameras, periscopes)
Describe the use of converging and diverging
lenses to correct long-sightedness and short-
sightedness
Nearsightedness, is corrected with a diverging lens. (Forms before retina)
Farsightedness, is corrected with a converging lens (forms behind retina)
Describe the dispersion of light as illustrated by the refraction of white light by a glass prism
It splits into it ROYGBIV colours
Uses of ultrasound in non-destructive testing of materials (2)
medical scanning of soft tissue
sonar (including calculation of depth or distance from time and wave speed)
How to correct long sightedness
Convex lens, so that the light rays are converged and can meet at the retina
How to correct short-sightedness
Concave lens, so that the light rays are diverged and can meet at the retina
