Physics Topic 6 - Waves Flashcards
What are two types of waves?
1-transverse
2-longitudinal
What is a transverse wave?
A wave for which the oscillations are perpendicular to the direction of energy transfer
What is a longitudinal wave?
A wave for which the oscillations are parallel to the direction of energy transfer
Give two examples of transverse waves
1-electromagnetic waves
2-seismic s-waves
Give two examples of longitudinal waves
1-sound waves
2-seismic p-waves
What are the parts of a longitudinal wave called?
Compressions and rarefactions
What is a wave’s amplitude?
The maximum displacement of a point on a wave from its undisturbed position
What is a wavelength?
-the distance from a point on a wave to the same position on the adjacent wave
-most commonly peak to peak or trough to trough
What is the frequency of the wave?
The number of waves that pass a given point each second
What is the unit for frequency?
Hertz, Hz
What is wave speed?
The speed at which the wave moves or at which energy is transferred through a medium
What does a wave transfer?
Energy
What word is used to describe when a wave bounces off a surface?
Reflection
How do sound waves travel through a solid?
The particles in the solid vibrate and transfer kinetic energy through the material
What is the frequency range of human hearing?
20 Hz - 20kHz
What are ultrasound waves?
Waves which have a frequency higher that the upper limit of human hearing
Give an example use for ultrasound waves
Medical or industrial imaging
What natural event causes seismic waves to be produced? What types are produced?
-earthquakes
-they both produce p-waves and s-waves
State a difference between the mediums that p-waves and s-waves can travel through
-p-waves travel through both solids and liquids
-s-waves only travel through solids
What technique is used to detect objects in deep water and measure water depth?
-echo sounding
-high frequency sound waves are emitted, reflected and detected
-time difference between emission and detection, alongside wave speed, are used to calculate distances
What type of spectrum do electromagnetic waves form?
A continuous spectrum
Order the types of electromagnetic radiation from lowest to highest frequency
-radio waves
-microwaves
-infrared
-visible light
-ultraviolet
-x-rays
-gamma rays
How do the speeds of EM radiation differ in a vacuum and in air?
Electromagnetic waves all travel at the same speed in a vacuum and in air
What property of waves in different mediums causes refraction?
-velocity
-wave speed is slower in denser materials, causing refraction
In which direction (relative tot he normal) do waves refraction when entering a denser medium?
-they bend towards the normal
-the angle of refraction is less than the angle of incidence
What types of waves can be produced by oscillations in an electrical current?
Radio waves
How can radio waves create an alternating current in a circuit?
When radio waves are absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves
Where do gamma rays originate from?
They originate from changes in the nuclei of atoms
What health effects can ultraviolet waves cause?
-they can cause the skin to age prematurely
-they can increase the risk of developing skin cancer
What health effects can X-rays and gamma rays cause?
-they are ionising radiation so can cause mutations in genes
-they can lead to increased risk of developing various cancers
Give three practical uses for infrared radiation
1-electrical heaters
2-cooking food
3-infrared cameras
Give two practical uses for microwave radiation
1-satellite communications
2-cooking food
Give two practical uses for radio waves
1-television transmission
2-radio transmission
What wave phenomenon is used by lenses to form an image?
Refraction
How does a convex lens form an image?
Parallel rays of light are refracted and brought together at a point known as the principal focus
What is meant by the focal length of a lens?
The distance from the lens to the principal focus
What is the difference between the image produced by a concave and convex lens?
-convex lenses can produce real or virtual images
-concave lenses can only produce virtual images
Why does magnification not have a unit?
-it is the ratio between image height and object height
-ratios do not require units
What determine the colour of visible light waves?
The wavelength and frequency of the light waves
What colour of visible light has the highest frequency?
Blue
What colour of visible light has the largest wavelength?
Red
What is meant by the term ‘secular reflection’?
Reflection from a smooth surface in a single direction
What is meant by the term ‘diffuse reflection’?
Reflection from a rough surface which causes scattering
How does a red colour filter work?
-a red filter absorbs all wavelengths of light other than those in the red range of the spectrum
-this means only red light passes through the filter
What determines the colour of an opaque object?
-different objects reflect different wavelengths of light by different amounts
-the wavelengths that are most strongly reflected determine the colour
What happens tot he wavelengths of light that aren’t reflected by an opaque object?
Any wavelengths that aren’t absorbed by the object
What colour does an object appear if all wavelengths are reflected by equal amounts?
White
What colour does an object appear if all wavelengths are absorbed?
Black
What do all bodies emit and absorb?
Infrared radiation
What happens tot eh quantity of infrared radiation emitted by an object as temperature increases?
The hotter the object, the more infrared radiation it will emit
What is a perfect black body?
An object that absorbs all of the radiation that is incident upon it
How much radiation does a perfect black body reflect or transmit?
None
Why is a perfect black body the best possible emitter of radiation?
-it is a perfect absorber since it absorbs all radiation incident on it
-a perfect absorber is also a perfect emitter
Other than the intensity of radiation emitted, how does increasing the temperature of an object affect its emissions?
The wavelength distribution of any emission is dependent on the object’s temperature
What can be said about the rates of emission and absorption for a body at constant temperature?
The body is absorbing and emitting radiation at the same time
What can be said about the rates of emission and absorption for a body increasing in temperature?
The body is absorbing radiation faster than it is emitting it
Give two factors that affect the temperature of the earth
1-the earth’s rate of absorption and emission of radiation
2-the amount of reflection of radiation into space
