Waves Flashcards
Give a way to minimise X-Ray exposure during a scan of a vehicle containing people?
The people should step out or wear protective gear
Which type of EM wave is typically transmitted in optical fibres?
Visible light
What is the doppler effect?
The change in wavelength observed due to the source
In cool conditions, would the resistance rise or drop
Rise
Is the resistance high or low in the darkness?
high
Describe the direction of vibrations in a longitudinal wave
The vibrations are parallel to the direction of energy transfer
Which type of EM wave has the highest frequency
Gamma rays
Explain how an alternating current produces radio waves
Alternating current is made up of oscillating charges which produce oscillating electric and magnetic fields in the form of radio waves
Explain how microwaves heat food
Penetrates a few centimetres into the food before being absorbed by the water molecules. The energy from the absorbed microwaves causes the food to heat up
What are optical fibres used for in phone lines?
To carry data over long distances
Are all EM waves transverse
Yes
What are transverse waves
A wave in which the oscillations are perpendicular to the direction of energy transfer
Amplitude, Wavelength and Frequency definitions
Amplitude (dB) = maximum displacement of a point on the wave from its undisturbed position
Wavelength (lamda) = distance between the same point on two adjacent waves
Frequency (Hz) = number of complete waves passing a certain point per second
How to find the period of a wave in seconds
T = 1/f
T (period (s)) = 1/ f (frequency (hZ))
True or False? All waves can be absorbed, transmitted or reflected
True
true or false…all waves can be absorbed, transmitted or reflected?
true - what happens depends on the wavelength of the wave and the properties of the materials involved.
What is the one simple rule for ALL reflected waves?
Angle of Incidence = Angle of Reflection
what is the difference between specular and diffuse reflection?
specular happens when a wave is reflected in a single direction by a smooth surface.
diffuse reflection is when a wave is reflected by a rough surface and rays are scattered in lots of different directions.
Which type of EM wave is typically transmitted in optical fibres
Visible Light
State what type of EM radiation is used to send signals to satellites?
Microwaves
Give two damaging effects that gamma rays can have
- cell damage
- cancer
State the law of reflection
The angle of incidence is equal to the angle of reflection.
How to find the Gradient of a Distance-Time graph
change in d/change in t
How to find the Gradient of a Velocity-Time graph
change in v/change in t
Velocity equation
V = S/T
Velocity definition
the rate of change of displacement
Scalar
A quantity with magnitude but no direction
Vector
A quantity with magnitude and direction
Accelaration equation
A = v-u/t
V = final velocity
U = initial velocity
T = time
Acceleration definition
The rate of change of velocity
Critical angle equation
n = 1/sin C
GPE equation
m x g x h
GPE, equation triangle
Transverse wave definition
the vibrations are perpendicular to the direction of the energy transfer. (e.g light)
Longitudinal wave definition
the vibrations are parallel to the direction of energy transfer (e.g sound)
Reflection
Reflection happens when light bounces off an even surface.
Refraction
Refraction occurs when a wave slows down or speeds up at a boundary between two materials
Law of Reflection
Angle of incidence = Angle of Refraction
Efficiency percentage equation
(Useful energy output/ Total energy output) x 100
Law of energy
Energy can not be created or destroyed, only transferred between energy stores.
Mass symbol
m
Mass units
kg
Volume symbol
V
Volume units
m^3
Is distance a scalar or vector quantity?
Scalar
What is density?
Density is given by ρ=m/V, where the ρ is the Greek letter rho, not a p
What is the Pressure formula
pressure = force/area
state the formula linking pressure, force and area
P = F/A
