Unit 3 - Waves Flashcards
Transverse waves…?
Are waves that oscillate perpendicular to the direction of energy transfer.
↳ The energy transfer is perpendicular to wave motion
They can move in solids surface of liquids and vacuums (they don’t require a medium to travel) but not in liquids and gases.
Longitudinal waves..?
Are waves where the points along its length vibrate parallel to the direction of energy transfer.
↳ The energy transfer is in the same direction as the wave motion
They can move in solids, liquids and gases, but they can not move in a vacuum (since there are no particles)
What is the SI unit of frequency?
Hertz (Hz)
What is the SI unit of length?
Metres (m)
What is the SI unit of speed and velocity?
Metres per second (m/s)
What is the SI unit of time?
Seconds (s)
What unit is used when measuring angles?
Degrees
What is the definition of amplitude?
The maximum displacement of a wave from its rest (equilibrium) position.
What is the definition of wavefront?
It is an imaginary surface representing corresponding points of a wave that vibrate in unison.
What is the definition of frequency?
The number of waves that pass a given point in one second.
What is a period of a wave?
The amount of time it takes for a wave to complete one cycle.
What is the definition of wavelength?
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests or troughs.
What do waves transfer?
Waves transfer energy not matter.
What is an equation of a wavelength?
wave speed = frequency × wavelength
v = f × λ
What is an equation of frequency?
frequency = 1/ time period
f = 1/T
What is the doppler effect?
The apparent change in wavelength and frequency of a wave emitted by a moving source. This frequency change due to the relative motion between a source of sound or light and an observer.
What happens to frequency with movement?
- The frequency is increased when the source is moving towards the observer
- The frequency is decreased when the source is moving away from the observer
What waves can be reflected and refracted?
Both waves, longitudinal and transverse can be reflected and refracted.
The electromagnetic spectrum (lowest → highest frequency)
Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays
The colours of the visible spectrum (decreasing in wavelength)
Red, orange, yellow, green, blue, indigo, violet
- Red has the longest wavelength (and the lowest frequency and energy)
- Violet has the shortest wavelength (and the highest frequency and energy)
Trends in the electromagnetic spectrum (radio waves…gamma rays)
- The energy increases
- The wavelength decreases
- The frequency increases
Applications for radio waves
Broadcasting and communication (radio and TV)
Applications for microwaves
Cooking and communication (WiFi, mobile phones and satellites)
Applications for infrared
Heaters and night vision equipment
Applications for visible light
Optical fibres and photography
Applications for ultraviolet
Fluorescent lamps
Applications for x-rays
Observing the internal structure of objects and materials, including for medical applications
Applications for gamma rays
Sterilising food and medical equipment
Effects of excessive exposure to microwaves
Internal heating of body tissue
Effects of excessive exposure to infrared
Skin burns
Effects of excessive exposure to ultraviolet
Damage to surface cells and blindness
Effects of excessive exposure to gamma rays
Cancer, mutation
What is the law of reflection?
The angle of incidence equals the angle of reflection.
Refractive index formula
refractive index = sin i/ sin r
n = sin i/ sin r
Whats the hearing range for humans?
20 - 20000 Hz
