3 Waves Flashcards
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
Relationship between amplitude and loudness
The bigger the amplitude, the louder
Oscilloscope
An osciloscope displays waves
Order of colours in visible light
Red
Orange
Yellow
Green
Blue
Indigo
Violet
As go down frequency increases and wavelength decreasess
Electromagnetic spectrum
A continuous series/spectrum of waves with identical properties
They all travel at 300000000 km/s
They all transfer energy
They are all transverse
They can be reflected and refracted
Angle of incidence
- sin angle of incidence = sin angle of refraction x n
Angle of refraction
- sin angle of refraction = sin angle of incidence / n
