waves Flashcards
Give four ways of measuring waves
wavelength, frequency, amplitude, speed
What’s the difference between transverse and longitudinal waves?
In transverse waves the vibrations are at 90 degrees to direction in which energy is transferred. In longitudinal waves the vibrations are along the same direction as the transferred energy
What’s the equation for wave speed?
wave speed = frequency x wave length
Which sorts of waves are transverse and which are longitudinal?
Most waves are transverse, including light waves and all other EM waves. Longitudinal waves include sound and ultrasound waves
How are waves changed when they meet an obstacle?
- reflected (rebound off) 2. refracted (change in direction) 3. diffracted
What are the seven types of electromagnetic waves in decreasing order of wavelength?
radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays
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How does the colour of visible light vary with wavelength and frequency?
Red has longest wavelength and lowest frequency; violet has shortest wavelength and highest frequency
What are radio waves used for?
Mainly communications (radio and TV)
Give two uses of microwaves
- Satellite communication, including satellite TV and mobile phones 2. Cooking in microwave ovens (waves are absorbed by water molecules in food)
Give two uses of infrared radiation
- Creates heat - used in electrical heaters and grills 2. Heat of objects can be detected by night vision equipment
Give two uses of visible light
- Communication using optical fibres, data carried as pulses of light (eg telephones and broadband) 2. Photography (aperture controls how much light gets in, shutter speed controls how long the film is exposed)
What is ultraviolet light used for?
Used in fluorescent lamps (more energy efficient than filament light bulbs)
What are X-rays used for?
Seeing internal structure of objects and bodies. X-rays pass easily through flesh but not through bones
