P6 - Waves Flashcards
What is amplitude?
The maximum displacement of a point on a wave, away from it’s undisturbed position.
What is frequency?
The number of waves passing a particular point per second.
What is wave length?
The distance from one point on one wave to the equivalent point on an adjacent wave.
What is wave length measured in?
Lambda
What is a period?
The time it takes for a wave to complete a full cycle.
What is amplitude measured in?
Amps (A)
What is frequency measured in?
Hertz (Hz)
What are the 2 types of waves?
Longitudinal and transverse.
What is a longitudinal wave?
When the oscillations are parallel to the direction of energy transfer.
What is a transverse wave?
The oscillations are perpendicular to the direction of energy transfer.
What is an oscillation?
A vibration about a rest posistion.
What is Echo sounding?
Used to detect objects in deep water and detect water depth.
What is the limit of human hearing?
20,000 Hz (anything above this is called an ultrasound)
How do you measure wave length?
Place a metre ruler perpendicular to the waves shown on the card.
Measure across as many waves as you can.
Divide that length by the total number of waves.
How do you measure wave frequency?
Count the number of waves passing a chosen point over a given time.
Divide the number of counted waves by the given time period.
What is the normal?
An imaginary line drawn perpendicular to the plane.
What is the angle of incidence?
The angle between the incident (incoming ray) and the normal.
What is the angle of reflection?
The angle between the reflected ray (outgoing ray) and the normal.
What is a rule linking the angle of incidence and the angle of reflection?
Angle of incidence = angle of reflection
What is a specular reflection?
When a reflection surface is smooth so, waves are reflected in a single direction.
What is diffuse reflection?
When a reflection surface is rough, scattering occurs, meaning waves are reflected in different directions.
What is refraction?
The change of direction caused by waves changing speeds as they enter a different material.
What happens when a ray enters a more dense material?
It slows and moves towards the normal.
What happens when a ray enters a less dense material?
It speeds up and moves away from the normal.
Give 2 examples of transverse waves.
Electromagnetic waves.
Seismic s-waves.
Give 2 examples of longitudinal waves.
Sound waves.
Seismic p-waves.
What are the two parts of a longitudinal wave called?
Compressions and rarefactions.
What is meant by frequency 200 Hz?
200 waves pass a point per second.
What is wave speed?
The speed at which a wave moves or energy is transferred through a medium.
Meters traveled per second.
What does a wave transfer?
Energy.
What equation do you use to calculate wave speed?
Wave speed = Frequency x wave length
What is wave speed measured in?
m/s
How do sound waves travel though a solid?
The particles in a solid vibrate and transfer kinetic energy through a material.
What is the frequency range of human hearing?
20 Hz - 20 kHz
Give an example use for ultrasound waves?
Medical or industrial imaging.
What natural event produces seismic waves?
Earthquakes - produces both p-waves and s-waves.
What medium can p-waves travel through?
Solids and liquids.
What medium can s-waves travel through?
Only solids.
How does echo-sounding work?
High-frequency sound waves are emitted, reflected and detected.
Time difference between emission and detection (alongside wave speed) are used to calculate distances.
What are the 2 types of seismic waves?
P-waves and S-waves
What is the purpose of the pinna (in the ear)?
Gathers sound waves from the environment and directs them into the ear canal, where they cause the ear to vibrate.
What are the “small bones” names?
Hammer, anvil and the stirrup.
What is the function of the “small bones”?
Transmit vibrations to the cochlea.
What does the cochlea do?
Converts these vibrations into electrical signals.
What does the auditory nerve do?
Transport the electrical signals to the brain.
What seismic wave has a faster wave speed?
P-waves.
How do we know the mantel is solid from the study of seismic waves?
Both P-waves and S-waves can travel through.
How do we know the outer core is liquid from the study of seismic waves?
P-waves are refracted indicating a change in density.
S-waves don’t pass through.
How do we know the inner core is liquid from the study of seismic waves?
P-waves are refracted again, indicating a different medium.
What does the speed of seismic waves through a material depend on?
The density of the medium of which they travel through.
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?
EM 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.
What type of waves can be produced by oscillations in an electrical circuit?
Radio waves.
What are EM waves?
Transverse waves that transfer energy from the wave source to the absorber.
What type of spectrum to EM waves form?
A continuous spectrum of different wavelengths but are grouped in order of their wavelength and frequency.
What do we know about the waves at the lower end of the EM spectrum?
Long wavelength.
Low frequency.
Low energy.
What do we know about the waves at the upper end of the EM spectrum?
Short wavelength.
High frequency.
High energy.
How are radio waves produced?
Oscillating electrons.
What are the 2 types of radio waves?
Short waves.
Long waves.
Why can long wave radio signals travel long distances?
Because they diffract and follow the curvature of the earth.
Why can short wave radio signals travel long distances?
They do not diffract, but they reflect of the ionsphere.
Why are microwaves useful?
Because they are not absorbed by the atmosphere, so they can be used to transmit signals to and from satellites.
Where are radio waves used?
To transmit television, radio and commercial signals.
Where is infrared radiation used?
Electrical heaters
Cooking food
Infrared cameras and detectors.
How do X-rays work?
They are high frequency rays that are absorbed by dense body parts, such as bones, but pass through soft tissue.
Where are X-rays used?
In medical imaging.
When are gamma rays emitted?
When a nucleus becomes unstable.
What 3 types of EM waves have dangerous effects on body tissue?
Ultraviolet waves, X-rays and gamma rays. (top 3 on EM spectrum)
What can high-frequency EM waves do to the body?
Cause mutations to DNA which can lead to cancer.
What can ultraviolet waves do to the skin?
Cause it to age prematurely. Increase the risk of developing skin cancer.
What type of radiation are X-rays and gamma rays?
Ionising radiation, can cause cancer.
How many millisieverts in 1 sievert?
1000.
What is the velocity of all EM waves in a vacuum?
3 x 10 (power of 8)
What type of EM radiation transfers the most energy?
Gamma rays.
What type of EM radiation does every object emit?
Visible light.
How do microwaves heat up food?
Water molecules in food absorb the microwave causing it to heat up.
What is ultraviolet absorbed by?
The skin.
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.
Two examples of where microwaves are used.
Satellite communications.
Cooking food.
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.
What is a name for the point at which rays of light are brought together?
Principle focus.
What is meant by the focal length of a lens?
The distance from the lens to the principle focus.
What is the difference between the image produced of convex lenses and concave lenses?
Convex lenses can produce real or virtual images.
Concave lenses only produce virtual.
What determines the colour of visible light waves?
The wavelength and the frequency of the light waves.
What colour of visible light has the highest frequency?
Blue
What colour of visible light has the longest wavelength?
Red.
How does a red colour filter work?
It absorbs all wavelengths of light other than those in the red range of the spectrum.
Meaning only red light passes through the filter.
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 determines the colour of an object?
Different objects reflect different wavelengths of light by different amounts.
The wavelengths that are most strongly reflected determine the colour.
What happens to the wavelengths of light that aren’t reflected by an object?
They are absorbed by the object.
What do all bodies (objects) emit and absorb and why?
Infrared radiation. Because of the energy in their thermal energy stores.
What happens when an object is hotter than it’s surroundings?
It will emit more radiation than it absorbs, meaning it’s temperature will decrease.
What is a perfect black body?
An object that absorbs all radiation that is incident on 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?
A perfect absorber is a perfect emitter.
What 2 things depend on the temperature of an object?
Wavelength
Intensity of radiation emitted.
What can be said about the rates for absorption and emission for a body at a constant temperature?
The body is absorbing and emitting at the same rate.
What can be said about the rates for absorption and emission for a body increasing in temperature?
It is absorbing it faster than it is emitting it.
Give 2 factors that effect the temperature of the Earth.
The Earth’s rate of absorption and emission of radiation.
Amount of reflection into space.
Does a hotter object or a cooler object emit more radiation, in a given time?
Hotter object.
How does temperature link to wavelength?
Very hot objects emit shorter wavelength radiation than cooler objects.
What happens to the amount of short wavelength radiation emitted as the object gets hotter?
More short wavelength radiation is emitted.
What happens to the intensity of the radiation at higher temperatures?
It increases.
What does transmitted mean?
Passed through.
What happens when an object is cooler than it’s surroundings?
It will absorb more radiation than it emits. So it’s temperature will increase.
What type of radiation does the sun emit?
Short wavelength radiation such as visible light and ultraviolet.
What (on earth) reflects radiation?
Clouds
What happens to the radiation that is not reflected by the clouds?
Absorbed by the earth, causing it to heat up, and then emitted back into space.
What process traps the energy that is emitted back into space?
The greenhouse effect.
What does human activities mean for the Earth/ greenhouse effect?
More heat energy is trapped and less is radiated into space.
How can cloud cover mean that less energy is radiated into space?
Clouds can reflect infrared back to earth and prevent it from being radiated into space.
What part of the spectrum is the radiation emitted from the Earth’s surface in?
Infrared.
What is the net result of the greenhouse effect?
That the temperature of the Earth increases until there is the same amount of incoming radiation as there is outgoing radiation.
What is the difference between wave frequency and speed?
Wave speed is meters traveled per second.
Wave frequency refers to the number of cycles per second.
Where is velocity slowest - shallow or deep water?
Shallow
