3.1.1 - 3.1.7 - Waves and the Electromagnetic Spectrum Flashcards
What are the 2 types of waves?
Transverse
Longitudinal
What is a transverse wave?
Waves that vibrate or oscillate perpendicular to the direction of energy transfer
How does transverse waves work?
The energy transfer is perpendicular to the wave motion
They transfer energy, but not the particles of the medium
They can move in solids and on the surfaces of liquids but not inside liquids or gases
Some transverse waves (electromagnetic waves) can move in solids, liquids and gases and in a vacuum
What are the points on a wave called?
The highest above the rest position is called the peak, or crest
The lowest below the rest position is called the trough
What are some examples of a transverse wave?
Ripples on the surface of water
Vibrations in a guitar string
S-waves (a type of seismic wave)
Electromagnetic waves (such as radio, light, X-rays etc)
What is a longitudinal wave?
Waves where the points along its length vibrate parallel to the direction of energy transfer
How do Longitudinal waves work?
The energy transfer is in the same direction as the wave motion
They transfer energy, but not the particles of the medium
They can move in solids, liquids and gases
They can not move in a vacuum (since there are no particles)
What are the points for a longitudinal wave?
The key features of a longitudinal wave are where the points are:
Close together, called compressions
Spaced apart, called rarefactions
What are some examples of Longitudinal waves?
Sound waves
P-waves (a type of seismic wave)
Pressure waves caused by repeated movements in a liquid or gas
How are Longitudinal waves drawn?
Longitudinal waves are usually drawn as several lines to show that the wave is moving parallel to the direction of energy transfer
Drawing the lines closer together represents the compressions
Drawing the lines further apart represents the rarefactions
What are the differences between Transverse and Longitudinal waves?
Structure : Transverse : Peaks and troughs, Longitudinal : Compression and rarefactions
Vibration : Transverse : Perpendicular to the direction of energy transfer, Longitudinal : Parallel to the direction of energy transfer
Vacuum : Transverse : Can travel in a vacuum (electromagnetic), Longitudinal : Cannot travel in Vacuum
Material : Transverse : Can travel through solids and on the surface of liquids , Longitudinal : Can travel through solids liquids and gases
Density and pressure : Transverse : Constant density and pressure , Longitudinal : Changes in density and pressure
What are the differences between the speed of transverse and Longitudinal waves?
Transverse - Depends on the material travelling through
Longitudinal - Depends on material travelling through
How do waves transfer energy?
Waves transfer energy and information
Waves are described as oscillations or vibrations about a fixed point
For example, ripples cause particles of water to oscillate up and down
Sound waves cause particles of air to vibrate back and forth
In all cases, waves transfer energy without transferring matter
All waves transfer energy, but they do not transfer the particles of the medium
This means when a wave travels between two points, no matter actually travels with it, the points on the wave just vibrate back and forth about fixed positions
What are the important factors to have motion?
Amplitude
Wavelength
Frequency
Time Period
Wavefront
What is amplitude?
The distance from the undisturbed position to the peak or trough of a wave.
Amplitude is the maximum or minimum displacement from the undisturbed position
What are wave fronts?
Wavefronts are a useful way of picturing waves from above: each wavefront is used to represent a single wave
The arrow shows the direction the wave is moving and is sometimes called a ray
The space between each wavefront represents the wavelength
When the wavefronts are close together, this represents a wave with a short wavelength
When the wavefronts are far apart, this represents a wave with a long wavelength
How does the doppler effect work with a police car?
The waves at the front of the moving vehicle appear to be squashed together:
This means the wavelength decreases (and the frequency of the waves increases)
The waves behind the moving vehicle appear to be stretched out:
This means the wavelength increases (and the frequency of the waves decreases)
What is the electromagnetic spectrum?
The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
This order is shown in the diagram below from longest wavelength (lowest frequency) to shortest wavelength (highest frequency)
The higher the frequency, the higher the energy of the radiation
Radiation with higher energy is:
Highly ionising
Harmful to cells and tissues causing cancer (e.g. UV, X-rays, Gamma rays)
Radiation with lower energy is:
Useful for communications
Less harmful to humans
What is visible light?
Visible light is defined as the range of wavelengths which are visible to humans
Each colour within the visible light spectrum corresponds to a narrow band of wavelength and frequency
The different colours of waves correspond to different wavelengths:
Red has the longest wavelength (and the lowest frequency and energy)
Wavelength and frequency are inversely proportional, this means that:
An increase in wavelength is a decrease in frequency (towards the red end of the spectrum)
A decrease in wavelength is an increase in frequency (towards the violet end of the spectrum)
Violet has the shortest wavelength (and the highest frequency and energy)
What are the Applications of Electromagnetic waves?
Radio waves can be reflected from the earth’s atmosphere
Microwaves can penetrate the earths atmosphere
Infrared waves can undergo total internal reflection
Visible light cameras are set up to detect visible light
Ultra violet because of its fluoresces with ultraviolet lighting
X ray can penetrate soft tissues but not bone
Gamma rays because Gamma rays can kill bacteria
What are the dangers of EM waves?
