WAVES TEST Flashcards
What are longitudinal waves?
Vibrations or oscillations are along the direction in ehh have the energy or wave is moving
Need a medium to move Slinky like Direction of movement is flat Compressions- bunched up Rare fraction- spaced out sections
What are transverse waves?
Vibrates or oscillates at right angles to the direction in which the energy or wave is moving
Amplitude
Maximum movement of particles from their resting position
Wavelength
The distance between a particular point on a wave and the same point on the next wave (eg crest to crest)
Time period
The period of a wave is the time for a complete cycle of the waveform
Waves transfer energy and information without transferring matter
Mobile phones, satellites etc rely on waves
Relationship between the speed, frequency and wavelength of a wave
Wave speed = frequency ✖️ wavelength
Relationship between frequency and time period
Frequency = 1/time period
Use the relationships in different contexts including sound waves and electromagnetic waves
As all waves share properties- frequency, wavelength and velocity can be used to describe all waves
Electromagnetic spectrum
1 they all transfer energy
2 they are all transverse waves
3 they all travel at speed of light in a vacuum (3✖️10 to the 8 m/s
4 they can all be reflected, refracted and diffracted
Electromagnetic spectrum, in terms of frequency
Increasing frequency, decreasing wavelength
Radio waves ➡️ microwaves ➡️ infra red ➡️ visible light ➡️ ultraviolet ➡️ gamma rays
Seven colours of the visible spectrum
Red Orange Yellow Green Blue Indigo Violet
Red has the longest frequency and lowest frequency
Uses of electromagnetic radiations
Radio waves- communicating information ➡️ radio, television, music and encoded data
➡️ because they can travel quickly
➡️ can code information
➡️ can travel long distance through buildings and walls
➡️ it is not harmful
Microwaves- commonly used in microwaves ovens, carry signals to satellites, messages sent from mobile phones are also carried by microwaves
Infrared- used in remote controls , videos and stereo systems
Visible light- main use it to see
Ultraviolet- used in security markers, kills bacteria and hardens filings
X rays- often used in x Ray machines, airport security and can be used to scan building structures for cracks
Gamma rays- sterilising medical equipment and treat cancer using radiotherapy
Affects of electromagnetic spectrum waves
Microwaves➡️ internal heating Infrared➡️ skin burns Visible light➡️ eye damage X rays➡️ risk of cancer and cell damage Gamma rays➡️ cancer and mutations
What type of waves are light waves?
They are transverse waves which can be reflected and refraction
Which are omitted from luminous or non luminous objects
Law of reflection
The angle of incidence equals the angle of reflection
Properties of an image in a plane mirror
The image is as far behind the mirror or the object is in front
The image is the same size as the object
The image is virtual- it cannot be produced on a screen
The image is laterally inverted- the left and right side of image appear under interchanged
How construct ray diagrams
Always include➡️ object, observers eye/POV, plane mirror, image and rays passing the object
Experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms
The light bends towards the normal as it passes from low density to high density (air to glass). The light is refracted upon emerging from the glass, the light bends away from the normal as it passes for, a high to low density (glass to air)
1- place glass block on piece of paper
2- send two narrow light rays through glass
3- observe the paths of the two rays of light
4- vary the angle of incidence and measure the angle of refraction
Relationship between refractive index, angle of incidence and angle of refraction
Refractive index = sin I/ sin r
(or the bigger sign over the smaller sign eg refractive index could be bigger at 60 compared to that of the sin I at 30 so then it’s 60/30 )
What is the refractive index?
The ratio between the sine of the angle of incidence and the sine of the angle of refraction
- in a material, the refractive index is constant throughout
An experiment to determine the refractive index using a glass block
1- place glass block on white sheet of paper
2- mark border of block with pencil
3- at one border draw a normal and draw a line to use as the incidence Ray, then put light ray along the line and draw the refracted line on other side
4- using protractor, measure the angle of incidence and the angle of refraction
5- using sin I/sin r, calculate the refractive index.
What is total international reflection?
When light falls on the surface of a lighter medium from a denser medium at an angle of incidence greater than critical angle, then light does not refract?
Conditions needed for total internal reflection
Light should fall in the surface of lighter medium from denser medium
Angle of incidence must be greater than the critical angle
What are optical fibres?
They use the property of total international reflection, this is a very thin strand composed of two difference types of glass. The inner core is more dense than the outer one. All the fibres are narrow. Light entering the inner core always strikes the boundary of the two glasses at an angle greater than the critical angle. This technique is used to send data at light speed.
What is the critical angle?
When the angle of refraction is equal to 90, the angle of incidence is called the critical angle.
Relationship between critical angle and refractive index
Critical angle = 1/ refractive index
What are type of waves are sound waves?
They are longitudinal waves, which can be reflected, refracted and diffracted. They reflect when they bounce back from a surface so that the angle of incidence is equal to the angle of reflection.
A REFLECTED SOUND WAVE IS CALLED AN ECHO.
sound waves refract when it changes direction when travelling across a high density medium
Sound waves are diffracted when they spread while travelling through a narrow space such as a doorway
What is our frequency range of hearing?
20-20,000 Hertz
This is our audible range.
Describe an experiment to measure the speed of sound in air
1- measure a large distance in an open field
2- first observer fires a starting pistol
3- second observer seeing the flash of the pistol, starts the stopwatch and then measures time until they hear sound
THIS IS CALLED THE SPEED OF SOUND
