Topic 1: Waves Flashcards
Wavelength
The length from peak to peak or trough to trough. Symbol: λ (lambda) Unit: m (meters)
Frequency
The number of waves passing a point each second. Symbol: f Unit: Hz Formula : f = N/t
Amplitude
The height of a wave from the centre to peak or trough. Symbol: A Unit: m (meters)
Louder wave
Increase in volume Increase in amplitude (same wavelength)
Quieter wave
Decrease in volume Decrease in amplitude (same wavelength)
Longitudinal waves
Vibrates along the same direction as the direction of travel and energy
Wavespeed unit (V)
Meters per second (ms-1)
Distance unit (d)
Meters (m)
Sources of error
Measuring distance and reaction time
In solids, vibrations are…
Passed on much quicker
Reflection
The bouncing back of a wave when it hits a surface through which it cannot pass.
More dense to less dense (glass to air)
Will speed up and the angle to the normal will bend away from the normal
Electromagnetic spectrum
All of the frequencies or wavelengths of electromagnetic radiation
Radio waves
Electromagnetic waves with the longest wavelengths and lowest frequencies. Used in television signals
Microwaves
Used in cooking, mobile phones. Can cause internal heating of body issues.
Ultraviolet
Can cause severe sunburn and damage to cells. Found in sunlight and artificial sources.
Gamma
Kills cancer cells, also damages cells. Found in neutron stars and supernove explosions. Waves with the highest frequency and the shortest wavelength.
Wavespeed
The speed of a wave, symbol is V (velocity) and is measured in meters per second.
High frequency wave
Increase in frequency Decrease in wavelength (same amplitude)
Low frequency wave
Decrease in frequency Increase in wavelength (same amplitude)
Wavespeed formula
V = fλ
Frequency formula
F = N/t
Transverse waves
Waves that vibrates at right angles of travel and energy
Frequency unit (f)
Hertz (Hz)
Wavelength unit (λ)
Meters (m)
Time unit (t)
Seconds (s)
All sound is…
Carried by vibrations
Law of reflection
Angle of incidence = angle of reflection
Where are the angles of incidence and reflection measured from?
Between the light ray and the normal
Refraction
Is the change of direction of a wave at a boundary. Always changes speed and sometimes direction.
Normal
A line that is always right angles to the boundary. All angles are measured to this line
Specular reflection
Reflection from a smooth surface
Diffuse reflection
Reflection from a rough surface
When does refraction occur?
When a wave goes from one medium to another and it always changes speed and sometimes changes direction
Why does an object appear to bend in water?
Because of refraction
Less dense to more dense (air to glass)
Will slow down and the angle to the normal will bend towards it
Infrared
This has wavelengths that are longer than visible light, and can be felt as heat. Could cause skin to burn.
Visible
Able to be seen. Very intense light could damage the retina
Xray
Used in medical images of bones. Can damage cells and cell death. Found in radioactive elements and hot objects in space.
Ray diagram
Diagram used to represent how light travels, each ray has an arrow to show the direction of travel
Period formula
T = 1/f
Wave
An oscillation that transfers energy.
Pressure
Is the force per unit area and applied perpendicularly.
The more often or harder the collisions…
The greater the pressure
If the volume of gas decreases…
The pressure increases.
Formula for pressure
P = f/a
Pressure unit
Nm-2
Force unit
N (newtons)
Force is usually weight =
W = mg
What is the kelvin temperature?
Is a scale that is designed so that absolute zero is defined as 0K.
Lowest temperature you can reach
Absolute zero
Celsius to Kelvin
+273
Kelvin to Celsius
-273
As particles increase in temperature
They move faster
For a fixed mass and volume of gas, the absolute pressure is…
Directly proportional to the Kelvin temperature
When would molecules stop moving?
When at absolute zero (0K)
To increase pressure
Increase the force Have a smaller surface area
To decrease pressure
Decrease the force Have a larger surface area
