Separate Physics - 6.6 Flashcards
What two types of wave are there?
Transverse or longitudinal
Give an example of a transverse wave
- All electromagnetic waves
- A ripple on water
- A wave on a string
Give an example of a longitudinal wave
- Sound waves in air
- Ultrasound
- Shock waves (e.g. some seismic waves)
What vibrations do transverse waves have?
Perpendicular (the oscillations are perpendicular to the direction of energy transfer)
What vibrations do longitudinal waves have?
Parallel (the oscillations are parallel to the direction of energy transfer)
What do longitudinal waves show areas of?
Compression and rarefaction
What are waves?
Transfers of energy (the particles remain in the same place)
Describe the wave feature: amplitude
The maximum displacement of a point on the wave from its undisturbed position
Describe the wave feature: wavelength
The distance between the same point on two adjacent waves
Describe the wave feature: frequency
The number of complete waves passing a certain point in a second (1 Hz is 1 wave per second)
Describe the wave feature: period
The amount of time taken for a full cycle of the wave
What is wave speed?
The speed at which the energy is transferred (or the wave moves) through a medium
What is the wave equation all waves obey?
Separate Q. What can happen to waves at the boundary between two different materials?
They can be reflected, absorbed or transmitted
Separate Higher Q. What do sound waves, travelling through a solid, cause?
Vibrations within the solid
Separate Higher Q. What causes the sensation of sound?
Sound waves cause the ear drum and other parts to vibrate: causing the sensation of sound
Separate Higher Q. The is human hearing limited?
The conversion of sound waves to vibrations of solids works over a limited frequency range
Separate Higher Q. Give an example of a process which converts wave disturbances between sound waves and vibrations in a solid
The effect of sound waves on the ear drum
Separate Higher Q. What is the normal human hearing range?
20 Hz to 20 kHz
Separate Higher Q. Detecting and exploring structures which are hidden from direct observations can be accomplished how?
Differences in velocity, absorption and reflection between different types of wave in solids and liquids aid this
Separate Higher Q. What properties does ultrasound have?
A frequency higher than the upper limit of hearing for humans
Separate Higher Q. How do ultrasounds work?
Ultrasound waves are partially reflected when they meet a boundary between two different media: the time taken for the reflections to reach a detector determine the boundary distance
Separate Higher Q. Why are ultrasounds useful?
Medical and industrial imaging
Separate Higher Q. What produces seismic waves?
Earthquakes
Separate Higher Q. What are P-waves?
Longitudinal, seismic waves (travelling at different speeds between solids and liquids)
Separate Higher Q. What are S-waves?
Transverse, seismic waves (unable to pass through liquids)
Separate Higher Q. What do P-waves and S-waves provide evidence for?
The structure (and size) of the Earth’s core
Describe electromagnetic waves
Transverse waves which transfer energy from the source of the waves to an absorber
What do electromagnetic waves form?
A continuous spectrum
What velocity do electromagnetic waves travel at through a vacuum?
The same velocity
List the waves of the electromagnetic spectrum in order of wavelength and frequency
What EM waves can our eyes detect?
Visible light (only a limited range of the EM spectrum can be detected)
Higher Q. When wavelength varies, different substances may do what?
Absorb, transmit, refract or reflect the EM waves differently
Higher Q. What causes some effects, such as refraction?
The difference in velocity of a wave at the boundary between two different media
Higher Q. What can oscillations in electrical circuits cause?
Radio waves
Higher Q. How can radio waves themselves induce oscillations in an electrical circuit?
Radio waves can be absorbed, creating an alternating current with the same frequency as the radio wave itself
What can cause EM waves being generated or absorbed over a wide frequency range?
Changes in atoms and the nuclei of atoms
Where do gamma rays originate from?
Changes in the nucleus of an atom
What EM waves can have hazardous effects on human body tissue?
Ultraviolet waves, X-rays and gamma rays
What is a measure of the risk of harm resulting from an exposure of the body to radiation?
Radiation dose (sieverts (Sv))
How may millisieverts (mSv) are in one sievert (Sv)?
1000 millisieverts (mSv) = 1 sievert (Sv)
What danger does ultraviolet light pose?
Skin can age prematurely and increase the risk to skin cancers
What danger do X-rays and gamma rays pose?
They are ionising radiation: mutations of genes and cancers
What practical applications are there for radio waves?
Television and radio
What practical applications are there for microwaves?
Satellite communications and cooking food
What practical applications are there for infrared waves?
Electrical heaters, cooking food and infrared cameras
What practical applications are there for visible light?
Fibre optics
What practical applications are there for ultraviolet light?
Energy efficient lamps and sun-tanning
What practical applications are there for X-rays and gamma rays?
Medical imaging and treatments
Separate Q. How does a lens form an image?
Refracts light
Separate Q. In a convex lens, where are parallel rays of light brought to a focus?
At the principal focus
Separate Q. What is the focal length?
The distance from the lens to the principal focus
Separate Q. What are ray diagrams used for?
The formation of images by convex and concave lenses
Separate Q. What images can be produced by a convex lens?
Real or virtual
Separate Q. What image is produced by a concave lens?
Virtual
Separate Q. What image represents a convex lens?
Separate Q. What image represents a concave lens?
Separate Q. What does each colour within the visible light spectrum have?
Its own narrow band of wavelength and frequency
Separate Q. What is specular reflection?
Reflection from a smooth surface in a single direction
Separate Q. What is diffuse reflection?
Reflection from a rough surface, causing scattering
Separate Q. How do colour filters work?
They absorb certain wavelengths (and colour) and transmit other wavelengths (and colour)
Separate Q. What determines the colour of an opaque object?
Which wavelengths of light are more strongly reflected (wavelengths not reflected are absorbed)
Separate Q. What happens if all wavelengths are reflected equally in an object?
It appears white
Separate Q. What happens if all wavelengths are absorbed in an object?
It appears black
Separate Q. Objects that transmit light can be fall into what two categories?
Transparent or translucent objects
Separate Q. What do all bodies, no matter what temperature, do?
Emit and absorb infrared radiation
Separate Q. What happens to the infrared radiation of a hotter body?
The hotter the body the more infrared radiation radiated in a given time
Separate Q. What is a perfect black body?
An object that absorbs all of the radiation incident on it
Separate Q. Since a good absorber is also a good emitter what would a perfect black body be?
The best possible emitter
Separate Higher Q. How can the absorption and emission of a body at constant temperature be described?
The body is absorbing radiation at the same rate it is emitting it
Separate Higher Q. When the temperature of a body increases what happens?
The body absorbs radiation faster than it emits radiation
Separate Higher Q. What affects the temperature of the Earth?
The rate of absorption and emission of radiation, reflection into space, and radiation into space
