Waves Flashcards
What are the 2 types of waves
Longitudinal and transverse waves
What is amplitude
The maximum displacement a particle can be from its equilibrium position. It is measure in metres
What is Equilibrium position
The position where the particle is undisturbed. This is considered as the halfway point between the two maximum positions of displacement.
What is displacement
The distance a particle is away from its equilibrium position. This can be either positive or negative depending on the side it is on compared to the equilibrium position. Displacement is measured in metres.
What is wavelength
The distance between two consecutive corresponding points on a wave. It is measured in metres.
Symbols of:
Wavelength
Amplitude
Equilibrium position
Displacement
λ
A
E
x
Labels in a longitudinal wave
Compression: an area of high pressure in a longitudinal wave
Rarefaction: region of low pressure
How are wavelengths found in a longitudinal wave
From centre of compression/rarefaction to centre of compression/rarefaction
What do waves do?
Waves transfer energy and information without transferring any mass.
formula to find the speed of a wave
wave speed = distance/ time
Formula to find time period
time period = 1/frequency
what type of waves are EM waves?
longitudinal
What are the different EM waves from lowest to highest frequency
Radio waves
Micro waves
Infrared
Visible
UV
X-Ray
Gamma ray
What is the wavelength of radio waves
Between 1-100 Km
What is the speed of EM waves?
Speed of light - 3x10^8 m/s
What is the speed of sound?
Around 330 m/s
Who predicted that Radio waves exist and who proved it?
Radio waves were predicted to exist by James Clerk Maxwell and was proven by Heinrich Hertz
Radio waves are the only waves that can do what?
Radio waves are the only waves that can penetrate water at a significant depth, even if it is not much, which is why radio waves are used to communicate with submarines by sending binary signals of waves.
What are radio waves used for and why?
Communicating or sending information of a TV or radio. This is because of the very long wavelength radio waves can diffract and rebound off the ionsphere which other waves cannot do which allows radio waves to better reach some areas in the world.
Wavelength of a microwave
1mm-1m
How does a microwave heat up food?
The frequency of a microwave makes it in such a way that it heats up water molecules. This means that if there is no water in a microwave, nothing will heat up.
What are microwaves most used for?
mobile phones - mobile phones use microwaves to a base station which is used to connect. Microwaves are also used to communicate with satellites in space and for Wi-Fi
Who discovered infrared radiation?
William Herschel in 1800
How are infrared waves emitted?
Anything with heat emits infrared waves. Because of this, infrared cameras work as they can detect the heat signals in different areas and infrared waves are used in heating
A property of infrared waves
Infrared waves can be easily absorbed by surrounding objects which makes them effective in short range communications. They are used in TVs
When did visible light get its name?
When it was discovered that there were other EM waves because before then it was called light
How is visible light used to transfer information?
Fibre optic communications
Fibre optic communications need cables with some glass in it, as visible light bounces of glass.
What happens when white light is shone on a glass prism?
Because white light is made out of all the other colours and that colours refract different angles, the result would be similar to a rainbow. Isaac Newton proved that white light was made out of all the different lights.
What is the cause of suntan?
UV waves hitting skin
How do UV light bulbs work?
By the effect of florescence
Uses of UV light
killing germs, and used in security to check that bank notes are actually real
What is the frequency of UV waves?
Around 10^15 Hz
Who discovered X-rays and how did x-rays get its name?
Wilhelm Conrad Roentgen, a German scientist, who called it x-ray because he had no idea of what it was
Why can you see bones through x-rays?
X-rays pass through soft materials, but not bones
What are the uses of x-rays?
X-rays are used in hospitals for checking bone structure or fractures…, in dentists for teeth and in airport security.
What are the potential dangers of x-rays
X-rays increase the chance of getting cancer
Gamma rays are usually produced how?
When a radioactive nucleus in an atom starts to decay
Why are gamma rays so dangerous?
Because they have a very high frequency of 10^18 - 10^21 Hz, gamma rays have a lot of energy which leads to gamma rays ionizing atoms which is when it removes the electrons of atoms making them positively charged which can cause mutations in the cells DNA and can cause cancer
What are gamma rays used for?
Gamma rays are used to kill germs in fruits like strawberries to conserve them and to treat cancer via radiotherapy and to identify cancer
What are the types of UV light?
UV A, UV B, UV C, with UV A having the least energy and with UV C having the most energy
What is a normal line?
The line where the ray from the object hits the object / mirror…
What is refraction?
When visible light refracts when entering a different material because there is a different density and the frequency needs to stay the same so the wave changes direction and keeps the same frequency despite being slower. The light can refract towards or away from the normal line depending on the density of the new medium
Law of reflection:
The angle of incidence (i) is equal to the angle of reflection(r).
A normal line must be drawn at 90 degrees to the mirror and always put arrows on the ray diagram lines to show the direction.
