Waves Flashcards
What are the 2 types of waves?
Transverse
Longitudinal
What is a wave?
Transfer of energy from one place to the other
What happens in a transverse waves?
Oscillations are perpendicular to the direction of energy transfer
What happens in a longitudinal wave?
Oscillations are parallel to the direction of energy transfer
What do all waves have?
Frequency, amplitude, wavelength, period
Describe frequency
The number of waves passing a fixed point per second, measured in hertz
Describe amplitude.
The maximum displacement that any particle achieves from its undisturbed position in metres
Describe wavelength
The distance from one point on a wave to the equivalent point on the next wave in metres
Describe period
The time taken for one to complete oscillation in seconds
What is the speed of a wave?
The speed at which the energy is transferred
What do you do when constructing a ray diagram?
Rays must be drawn using a ruler
Single arrow
All relevant angles labelled
What does the direction of refraction depend on?
The angle at which the wave hits the boundary, the materials involved
What causes refraction?
The difference in the wave speed in the different media
What do sound waves have?
Frequency, amplitude and wavelength
What is the normal range of human hearing?
20Hz to 20,000Hz
What happens when sound waves reach the ear?
The ear drum vibrates
What frequency are ultrasonic waves?
greater than 20,000Hz, so they cannot be heard by human ears
What happens when an ultrasonic wave meets a boundary between two different media?
It is partially reflected
What is ultrasonic waves used for?
Pre-natal scanning, detection of kidney stones and tumours, and producing images of damaged ligaments and muscles
What are echo sounds used for?
Detecting objects in deep water and measuring the depth of water
What are the 2 types of seismic waves?
P-waves (primary)
S-waves (secondary)
What are P-waves?
Longitudinal waves
Travel at the speed of sound (double S-waves)
Travel at different speeds through solids and liquids
What are S-waves?
Transverse waves
Not able to travel through liquids
What happens during an earthquake?
Seismic waves travel outwards from the earthquake and are capable of travelling all the way through the Earth
Seismic waves travel in a curved path through the earth, due to the earth increasing in density with depth
Detectors placed around the earth measure when and where the different waves arrive
What happens in the S-wave shadow zone?
S-waves are not able to travel through the liquid outer core of the earth
This results in a large shadow zone on the opposite side of the earth to where the earthquake originated
What happens in the P-wave shadow zone?
P-waves are able to travel through the liquid outer core
They are refracted at the boundary between the semi-solid mantle and the liquid outer core
They are refracted again at the boundary between the liquid outer core and solid inner core
What are electromagnetic waves?
Transverse waves
What do electromagnetic waves travel through?
In air or a vacuum at the speed of light
How does the wavelength of an electromagnetic wave affect it?
Affects how it is absorbed, transmitted, reflected or refracted by different substances, changes his uses
What are radio waves caused by?
Oscillations in electrical circuits
What are the hazards of Electro magnetic waves?
Ultraviolet waves can cause the skin to age prematuarly and increase risk of skin cancer
X-rays and Gamma rays cause ionising radiation that can damage skin cells
What does a lens form?
An image by refracting light
What are the 2 main types of lens?
Concave
Convex
How is a convex lense structured?
Wider in the middle than at the edges
How is a concave lense structured?
Wider at the edges than it is in the middle
What do you do when drawing a ray diagram?
Principle axis
Use the correct lense symbol
Mark the principle foci on either side of the lens by drawing a dot on the principle axis and labelling it
Mark the position of the object as an arrow standing on the principle axis
Draw the light rays
What is magnification?
The ratio of image height to object height
What is visible light?
Describes electromagnetic waves that can be detected by the human eye
What is specular reflection?
Reflection by a smooth surface in a single direction
What is diffuse reflection?
Reflection from a rough surface, where the light is scattered
What do all bodies emit and absorb?
Infrared radiation
What does the rate at which an object emits radiation depend on?
The nature of the surface and on its temperature
What does the temperature of an object depend on?
The rate at which it emits radiation
The wavelength of the radiation it emits
What is the temperature of an object related to?
the balance between radiation absorbed and radiation emitted
What does the temperature of the earth depend on?
How much energy it recieves from the sun
How much energy is reflected back into space
How much energy it emits into space
