Transverse Wave
Oscillates perpendicular to the direction of travel and energy
Longitudonal Wave
A wave in which oscilates parallel to the direction of travel and energy
Amplitude
The maximum displacement of a point of a wave from rest point
Frequency
The number of waves that pass through a point each second. Mesured in hertz (Hz)
Wavelength
Distance covered by a full cycle of a wave. Measured from crest to crest in metres (M).
Time period
The time taken for a full cycle of a wave
Wavefront
This is an imaginary surface that we draw to represent the vibrating part of a wave
How do waves transfer energy
Waves transfer energy without transferring mass
Calculate wave speed
wave speed (m/s) = frequency (Hz) x wavelength (m)
Calculate frequency
frequency (Hz) = 1 / time period (s)
Calculate time period
time period (s) = 1 / frequency (Hz)
Doppler effect
Can be observed when a wave is moving relative to the observer. There is a change in wavelength and frequency. At the front there is a small wavelength and high frequency. At the back there is a long wavelength and a low frequency.
Waves and order of the electromagnetic spectrum
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet (UV
X-ray
Gamma rays
As you go down frequency increases and wavelength decreases.
They are transverse
Uses of waves in electromagnetic spectrum
- radio waves: broadcasting and communications
- microwaves: cooking and satellite transmissions
- infrared: heaters and night vision equipment
- visible light: optical fibres and photography
- ultraviolet: fluorescent lamps, detecting forged bank notes
- x-rays: observing the internal structure of objects and materials, including for
medical applications - gamma rays: sterilising food and medical equipment.
Dangers of waves
- microwaves: internal heating of body tissue
- infrared: skin burns
- ultraviolet: damage to surface cells and blindness
- gamma rays: cancer, mutation
Law of reflection
Angle of incidence (i) = angle of reflection (r)
Total Internal Reflection (TIR)
Light bounces off a boundary instead of going through it. This happens when angle i is greater than critical angle. Only happens when traveling from more dense to less dense
When angle i is equal to critical angle…
Refracted ray carries along the boundary
Refraction
When angle i is smaler than critical angle
From less dense to more dense, towards normal
From more dense to less dense, away from normal
Critical angle
- sin critical angle = 1 / refractive index
- Bigger than 20º
Refractive index
- Refractive index(n) = 1 / sin critical angle
- Refractive index(n) = sin i /sin r
- No unit: Only number/ratio
- Bigger than 1
Sound waves…
- Longitudinal
- Can be refracted or reflected
Hearing range for humans
20 Hz - 20000 Hz
Relationship between frequency and pitch
The higher the frequency, the higher the pitch
