Waves Flashcards
Unit for angle
degree (°)
Unit for frequency
hertz (Hz)
Unit for wavelength
metre (m)
Unit for velocity
metre/second (m/s)
Unit for time
second (s)
Explain the movement of a longitudinal wave
Longitudinal waves is a wave that vibrates or oscillates at parallel to (along) the direction in which the wave is moving.
Explain the movement of a tranverse wave
Transverse waves is a wave that vibrates or oscillates at right angles (perpendicular) to the direction in which the wave is moving.
Explain the difference between a transverse wave and a longitudinal wave
A longitudinal wave has vibrations parallel to the direction of the wave meanwhile transverse waves has vibrations at right angles to the direction of the wave
Wavefront
A way of seeing waves from above
Amplitude
This is the distance from the midpoint to the peak of a wave
Wavelength
This is the distance between two corresponding points on the wave and is measured in metres
Frequency
This is how many waves pass by a point every second and is measured in Hertz (Hz)
Time period
The time it takes for one complete wave to pass a particular point
What can waves transfer?
Waves can transfer energy and information with out transferring matter
Give an example of a wave that transfers energy
Sun light, it transfers energy as it makes the earth warm without bringing any matter.
What is the relationship between the speed, frequency and wavelength of a wave: v = f × λ
Wave speed (v) = frequency (f) x wavelength (λ)
Give the units for the wave equation
Wave speed (m/s) = frequency (Hz) x Wavelength (m)
What is the relationship between frequency and time period: time period x frequency = 1 or f = 1/T
Time period(T) = 1 / frequency (f) Frequency (f) = 1 / time period (T) 1 = frequency (f) x time period (T)
Doppler effect
When an object is moving toward you the waves from the object compress and you hear this as a higher frequency. When an object is moving away from you the waves strech out and you hear this as a lower frequency. The greater the speed of the moving object the greater the change in frequency. The sound the leaves the speaker is always the same, it is only different to the observer
Properties of electromagnetic waves
Transfer energy
Are transverse waves
Travel at the speed of light in a vacuum
Can be reflected and refracted
Electromagnetic waves (from low to high frequency)
Radio waves Micro waves Infra red Visible light Ultra-violet X-rays Gamma rays
Uses of Radio waves
broadcasting and communications
Uses of Microwaves
cooking and satellite transmissions
Uses of infra red
remote controls and night vision equipment
Uses of visible light
optical fibres and photography
Uses of ultraviolet
fluorescent lamps and killing bacteria
Uses of X-rays
observing the internal structure of objects and materials, including for medical applications
Uses of gamma rays
sterilising surgical equipment and medical equipment
Danger of microwaves
internal heating of body tissue
Danger of infrared
skin burns
Danger of ultraviolet and protective measures
damage to surface cells and blindness; wear sun glasses, sun cream and stay in shade for UV
Danger of gamma rays and protective measures
cancer, mutation; avoid exposure and wear suitable protective clothing
Light is…
a transverse wave and can be reflected and refracted
Reflection
When light reflects off a mirror the angle of incidence always equals the angle of reflection
Refraction
When light enters a medium of different density is changes speed and direction. This change in direction is known as refraction
The role of total internal reflection
Total internal reflection is used to transmit signals along optical fibres.
When happens refraction
angle of incidence < critical angle
When happens critical case
angle of incidence = critical angle
When happens TIR
angle of incidence > critical angle
What is required for TIR to occur
The ray of light must be travelling from a more dense to a less dense medium.
The angle of incidence must be greater than the critical angle.
Snell’s law
n = sin i / sin r
Critical angle
When light is refracted and passes along the boundary of the surface
The relationship between critical angle and refractive index
C = sin-1(1/n) n = 1 / sinC
longitudinal waves can…
be reflected and refracted
Practical to find the refractive index and the critical angle of a glass block
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Calculate the refractive
index - Repeat steps 2 – 7 using a different angle of
incidence - Find an average of your results.
