Waves Flashcards
Wavelength, λ
Distance from a point on a wave to an identical point on the next wave. Measured in metres (m)
Amplitude
Size of maximum disturbance from the centre line
Period, T
Time taken for one full wave to pass a point Measured in seconds (s)
Wave speed, v
Distance travelled by a wavelength in one second Measure in metres per second (m s-1)
Wave Speed, v - formula
wavespeed = distance travelled/time
or
wavespeed = wavelength/period
Frequency, f
Number of waves passing a fixed point every second Measured in hertz (Hz)
Frequency, f - formula
frequency = number of waves/time
or
frequency = 1/period
The Wave Equation
The wave equation links the speed, frequency and wavelength of a wave in one equation.
speed = frequency x wavelenth v = fλ
or
speed = distance/time v = d/t
Types of Waves
Transverse waves -
With transverse waves, the motion of the particles (or medium) is at right angles to the direction of motion of the wave.
Examples of transverse waves include water waves and electromagnetic waves
Longitudinal waves -
With longitudinal waves, the motion of the particles (or medium) is in the same direction as the direction of motion of the wave. Examples of longitudinal waves include sound waves and shock waves
Speed of Sound in Air
Under normal conditions, the speed of sound in air is measured as 340 m s-1. That means it can travel over 1km in 3 seconds. We can use this to predict the distance of a lightning strike. For ever 3 seconds between the “flash” and the “crash”, the sound has had to travel over 1 km.
Comparing Sound Waves
Waves of different amplitude and frequency will sound different. When displayed on an oscilloscope they will also look different
Quiet Sound - Low Amplitude
Loud Sound - High Amplitude
Low Pitch - Low Frequency
High Pitch - High Frequency
The Electromagnetic Spectrum
The electromagnetic spectrum is a family of electromagnetic waves which all travel at the speed of light, 3x108 ms-1.
All EM waves are transverse waves. Except for their speed, each part of the spectrum demonstrates different properties and therefore different applicationsas well as potential hazards.
Order of Waves
Gamma Rays (high frequency, high energy, low wavelength)
X-Rays
Ultraviolet Light
Visible Spectrum
Infrared
Microwave
Radiowaves (low frequency, low energy, high wavelength)
Gamma Rays - Uses
Treatment of cancers, through radiotherapy. Tracers, as rays are very penetrative but less ionizing than alpha or beta radiation (see Nuclear Physics in S4). Sterilisation of medical equipment
X-Rays - Uses
Non-invasive/surgical method to locate/identify broken bones and other abnormalities within the body.
Ultraviolet - Uses
Used in the treatment of skin problems and sterilization of equipment.
Visible - Uses
Medical applications include lasers. Knowledge of light allows the development of glasses, endoscopes and optical fibres
Infrared - Uses
This is radiated heat. Used in physiotherapy and can be detected and displayed as thermograms, identifying injuries or heat loss in homes.
Microwaves - Uses
Used in communications as well as the heating of foods
Radiowaves - Uses
Mainly used in communications and radar
Refraction of Light
refraction occurs when light passes from one transparent medium to another. when this happens, the light will experience a change in speed and wavelength but not frequency. this is known as refraction. there may also be a change in direction of the light when at an angle from the normal
when light passes into a fender medium the angle of refraction (r) is less than the angle of incidence (i). all angles are measured from the normal line
diffraction
all types of waves are able to diffract if they have large enough wavelengths. due to their long wavelength (low frequency) radio waves are able to diffract round large object such as mountains.
