Paper 1 - Waves Flashcards
What are the differences between digital and analogue signals?
- analogue is continuously varying
- digital has only discrete values
- digital is less prone to interference than analogue
- digital can be processed more easily than analogue by a computer
What happens when a metal aerial absorbs radio waves?
- creates an alternating current
- with the same frequency as the radio wave
What properties that all electromagnetic waves have?
- travel at the same speed in a vacuum
- can be refracted/reflected
- transfer energy
- can be absorbed
What is the correct order of the electromagnetic spectrum?
Radio → Micro → Visible light → UV → X-Rays → Gamma
Define amplitude`
The distance between a peak and an equilibrium
Define wavelength
The distance from one point on a wave to the same spot on the next wave
Define trough
The maximum value of downward displacement within a wave cycle
Define crest
The maximum value of upward displacement within a wave cycle
Give an example of longitudinal waves
- Sound waves
- Seismic P Waves
What properties can be obtained from a displacement-velocity graph of a wave?
- Amplitude
- Frequency
- Wavelength
- Wave speed
How does the direction of energy transfer relate to the direction of particle vibration in a transverse wave?
In a transverse wave, the direction of energy transfer is perpendicular to the direction of particle vibration
How does the direction of energy transfer relate to the direction of particle vibration in a longitudinal wave?
In a longitudinal wave, t he direction of energy transfer is parallel to the direction of particle vibration
Define compression
The point in a longitudinal wave cycle in which the particles are closest together
What properties can be obtained from a displacement-time graph of a wave?
- Amplitude
- Frequency
- Time period
- Wavelength
- Wave speed
Give an example of a transverse wave
- Electromagnetic waves
- S waves
Define wavefront
A surface containing points affected in the same way by a wave at a given time.
What do waves transfer and without what?
Waves transfer energy and information without transferring matter
What is the relationship between = wave speed, frequency and wavelength?
v = f x λ
What the relationship between frequency and time period?
f = 1 / t
Why there is a change in the observed frequency and wavelength of a wave
when its source is moving relative to an observer?
- This is known as the doppler effect
- The wavelength gets shorter
- The frequency increases
- So the pitch increases
What are radio waves used for?
Broadcasting and communications
What are microwaves used for?
- Cooking
- Satellite transmissions
What are infrared waves used for?
- Heaters
- Night vision equipment
What are visible light rays used for?
- Optical fibres
- Photography
What are ultraviolet rays used for?
Florescent lamps
What are X-rays used for?
Observing the internal structure of objects and materials including for medical applications
What are gamma rays used for?
- Sterilising food
- Sterilising medical equipment
- Destroying cancer cells
What are the detrimental effects of excessive exposure of the human body to microwaves?
Internal heating of body tissue
What are the detrimental effects of excessive exposure of the human body to infrared radiation?
Skin burns
What are the detrimental effects of excessive exposure of the human body to ultraviolet rays ?
- Damage to surface cells
- Blindness
What are the detrimental effects of excessive exposure of the human body to gamma rays?
- Cancer
- Mutation
Describe simple protective measure against the risks
- Wear goggles
- Wear gloves
- Minimise exposure time
- Maximise distance away from the electromagnetic wave
Give 2 properties about light waves
- They are transverse
- They can be reflected and refracted
When does total internal reflection occur?
When the angle of incidence equals the angle of reflection
What is the equation for refractive index?
n = sin i / sin r
Describe the role of total internal reflection in transmitting information along optical fibres and in prisms
Total Internal Reflection is used to transmit signals along optical fibres
Explain the meaning of critical angle c
The angle (specific to the medium) that, if the angle of incidence is equal to c, then the angle of refraction is 90°
What is the equation for the critical angle
sin c = 1 / n
Explain the path of a ray of light in an optical fibre
- Total internal reflection occurs
- The core has a higher refractive index than air
- Angle of incidence is greater than the critical angle
- Light travels more slowly in glass
What is a hazard of microwave radiation?
Internal heating of tissue
State the name of an electromagnetic wave with a wavelength longer than microwave radiation
Radio
