P1 Flashcards
What is a wave?
A regular disturbance that transfers energy
What is the amplitude of a wave?
The distance between the rest position and crest or trough
What is the wave length of a wave?
The distance between the same point on two neighbouring disturbances (one full cycle)
What is the frequency of a wave?
The number of complete waves placing through a point per second (measured in Hz)
What is the period of a wave?
The time it takes to complete one cycle- it is inversely proportionate to frequency
What is the medium of a wave?
Any substance that carries the wave, or through which the wave travels
What are some examples of transverse waves?
EM waves, S waves, Waves in water
What are some examples of longitudinal waves?
Sound waves, P waves
What direction is the disturbance of the medium to the direction of the wave in transverse waves?
Perpendicular (at 90 degrees)
What direction is the disturbance of the medium to the direction of the wave in longitudinal waves?
Parallel
In longitudinal waves, what is the point of high pressure (lots of particles) called?
Compressions
In longitudinal waves, what is the point of low pressure (fewer particles) called?
Rarefactions
What is the formula for wave speed?
Wave speed (m/s) = Frequency (Hz) x Wavelength (m)
What apparatus can you use to measure the speed of sound?
An oscilloscope, a speaker attached to a signal generator and two microphones
Describe the experiment to measure the speed of sound
1) Set up the oscilloscope so the detected waves at each mic are shown as separate waves
2) Start with both mics next to the speaker, then slowly move one away until the waves are aligned on the display, but have moved exactly one wavelength apart
3) Measure the distance between the two mics to find the wavelength
4) The frequency is whatever you set the signal generator to
5) Use the formula [Wave speed (m/s) = Frequency (Hz) x Wavelength (m)] to find out the speed of the wave (sound)
What are the 3 things that can happen when a wave meets a new boundary?
It can be absorbed, transmitted or reflected
What is it when a wave is absorbed?
The wave’s energy is transferred to the new material, often causing heating
What is it when a wave is transmitted?
The wave carries travelling through the new material, often causing refraction
What is it when a wave is reflected?
The wave is sent back away from the new material
What is the relationship between angle of incidence and angle of reflection?
Angle of incidence = Angle of reflection
What is refraction?
A change in the speed of which the wave is travelling, which when at an angle to the normal, causes a change in direction
Can the frequency of a wave change?
No
If the wave slows down, what is the effect on the wave length and why?
The wave length will also decrease, as speed = frequency x wavelength, therefore if speed decreases, and frequency cannot change, the wavelength must also decrease
If the wave speeds up, what is the effect on the wave length and why?
The wave length will also increase, as speed = frequency x wavelength, therefore if speed increases, and frequency cannot change, the wavelength must also increase
What is the normal?
A line drawn at a right angle to the boundary
What is the relationship between wavelength and frequency of EM waves?
As wavelength increases, frequency decreases
What is the wavelength of radio waves?
1m - 10^4 m
What is the wavelength of micro waves?
10^-2 m
What is the wavelength of infrared waves?
10^-5 m
What is the wavelength of visible light waves?
10^-7 m
What is the wavelength of ultra violet waves?
10^-8m
What is the wavelength of x-ray waves?
10^-10
What is the wavelength of gamma waves?
10^-15
What is another word for different energy levels in an atom?
Shells
What can EM radiation cause (in relation to electrons and shells)?
An electron can move up one or more energy levels (shells) when EM radiation with the right amount of energy
What is the relationship between frequency and energy in EM radiation?
As frequency increases, so does energy
What happens after an electron is “excited” and moves up an energy level/s?
The electron will fall back to it’s original level, and in doing so will release the energy it absorbed previously- this energy is carried away by EM radiation
What is an ionised atom?
An atom that has lost an electron/s
How does high amounts of exposure ionising radiation cause damage?
Ionising radiation contain enough energy to knock electrons off some atoms- these ionised atoms can then go on to react further, causing possible cellular damage / destruction
How does low amounts of exposure ionising radiation cause damage?
Ionising radiation can cause cellular mutations, making cell more likely to grow in an uncontrolled way, possible leading to cancer
State one use of radio waves
To transmit information (e.g. TV or radio shows)
State one use of micro waves
For cooking
How do micro waves cook food?
The radiation penetrates into the food before being absorbed, which then transfers energy to the water molecules, causing the water to heat up. This then heats up the rest of the food, which quickly cooks
State one use of infrared radiation
For monitoring temperature
State one use of visible light
To allow us to see
State one use of UV radiation
Used in florescent lamps
State one use of X-rays
To allow to inside things
State one use of gamma rays
For sterilising equipment
All objects emit EM radiation (true or false)
True
All objects absorb EM radiation (true or false)
True
The balance between absorbed and emitted radiation affects what?
The temperature of an object
Why do objects cool down?
Because they are emitting more radiation than they are absorbing
Why do objects heat up?
Because they are absorbing more radiation than they are emitting
What happens when an object is emitting and absorbing the same amount?
The temperature stays the same
What is principal frequency?
The frequency of radiation that an object emits the most of
What is the relationship between principal frequency and temperature?
As principal temperature increases, so does principal frequency
What is the relationship between principal wavelength and temperature?
As principal temperature increases, principal wavelength decreases
Explain the greenhouse effect
Greenhouse gases absorb lower frequency radiation, meaning they absorb a lot of the radiation emitted by the Earth (as it has a lower principal frequency as it is cooler), and absorb little of the radiation emitted by the Sun (as it has a higher principal frequency as it is hotter).
This means that radiation is trapped in the Earth’s atmosphere, meaning the radiation will be absorbed again, increasing Earth’s temperature.
The more greenhouse gases, the more this occurs, the hotter Earth gets
What are the most common human impacts on greenhouse gas levels?
Deforestation- less CO2 absorbed
Burning fossil fuels- more CO2 emitted
Agriculture- more Methane emitted
Decaying waste- more Methane emitted
What is specular reflection?
When parallel incident waves are reflected in a single direction by a smooth surface (e.g. a mirror)
What is scattered reflection?
When parallel incident waves are reflected in all different directions by an uneven surface (e.g. paper)
If a light ray slows down as it crosses a boundary, will it bend away or towards the normal?
It will bend towards the normal
If a light ray speeds up as it crosses a boundary, will it bend away or towards the normal?
It will bend away from the normal
If a light ray travels through a rectangular block, the incident and emerging ray will not be parallel (true or false)
False, they will be parallel
Different wavelengths of light travel at different speeds in air
False, they travel at the same speed in air
Different wavelengths of light travel at different speeds in different mediums
True
State the order of the colours of light in order of increasing wavelength
Shortest wavelength -Violet, Indigo, Blue, Green, Yellow, Orange, Red- Longest wavelength
What is the relationship between wavelength and speed and amount of refraction?
The shorter the wavelength, the slower the speed, the more it refracts`
Which will refract more, blue or green light?
Blue, because it has a shorter wavelength
What do colour filters do?
Let through particular wavelengths
What causes sound waves to form?
Vibrating objects
What happens when a sound wave travels through a solid?
It causes the particles in the solid to vibrate
In which medium do sound waves travel the fastest and the slowest?
Fastest: Solids
Slowest: Gasses
Why can’t sound waves travel in space?
Because there is no particles to move or vibrate
What frequency counts as ‘ultrasounds’?
20,000 Hz +
State three uses of ultrasounds
Medical imaging
Industrial imaging
SONAR (used by boats and submarines to find out the distance of things)
What type of waves do earthquakes and explosions cause?
Seismic waves
What are three types of seismic waves?
P-Waves, S-Waves and L-Waves
What are L-Waves?
Waves that travel along the surface of the Earth, moving the ground up and down
What are P-Waves and what are their properties?
- Longitudinal
- Travel through solids and liquids
- Travel faster than S-Waves
What are S-Waves and what are their properties?
- Transverse
- Travel through solids
- Travel slower than P-Waves
How can we use seismic waves to investigate the structure of the Earth?
We can detect where certain waves are detected and where they are not, and make conclusions from their properties about the structure of the Earth
For example- S-Waves produced at the North Pole will not be detected at the South Pole, and given the fact that S-Waves cannot travel through liquids, we can conclude that a portion of the Earths inside is liquid
