Waves and EM Spectrum Flashcards
What are waves?
Waves (vibrations) are a way of transferring energy with no matter being transferred
What are wavefronts?
Points on a surface where all vibrations are in phase and the same distance from the source
What are transverse waves?
Vibrations occur at right angles to the direction in which the wave is travelling
Examples of transverse waves:
Water waves
Light waves
Earthquake waves
What are longitudinal waves?
Vibrations occur at parallel to the direction in which the wave is travelling.
Includes areas of compression and rarefaction
Examples of longitudinal waves:
Sound waves
What is wavelength?
The distance from two consecutive peaks/troughs of a wave is called the wavelength
What is amplitude?
Amplitude is the maximum distance moved by a vibrating object from its equilibrium position
What is time period?
Time taken to make one complete oscillation
What is frequency?
The number of waves or vibrations passing a point per second
The relation between frequency and time period
F = 1/T
Wave Equation:
*Note the relation between frequency and wavelength (while wave speed is constant)
wave speed = frequency x wavelength
Law of Reflection?
The angle of incidence is equal to the angle of reflection
Properties of EM waves:
- Transfer energy
- Transverse waves
- Travel at the speed of light in a vacuum
- They can all be reflected and refracted
Order of waves:
Graham’s Xylophone Uses Very Interesting Musical Rhythms
Wavelength and frequency of waves in the EM spectrum:
G ➡ R
Increase in wavelength
Decrease in frequency
Uses of gamma rays:
- Sterilising medical equipment
- Irradiation
- Treat cancer (radiotherapy)
Uses of X-rays:
- Medical images (radiographs) of bones
- In airports to scan luggage
- In industry to check for cracks and faults in machinery and buildings
Uses of UV rays:
- Causes tan (tanning beds)
- Some chemicals glow when under UV light - security marker pens
- Detecting counterfeit notes
- Fluorescent tubes: mercury vapor emits UV which strikes the fluorescent powder coating the inside of the tube, which then emits visible light
Harmful effects of UV rays
- Sunburn and blistering
- Skin cancer
- Blindness
Protection against UV rays:
- Protective goggles/ glasses
- Skin creams
Uses of visible light:
- Seeing
- Used to read barcodes and compact disks
- Used to read information stored on DVDs
- Telecommunications: optical fibres
- Photography
Uses of IR waves:
- Remote controls
- Cooking
- Electric fires, heaters
- Night vision
Properties specific to IR:
- not very harmful (skin burns)
- Low penetrating power ➡ small distances ➡ interference with other signals waves is unlikely
