Waves Flashcards
2 types of waves
Transverse and lognitudinal
wave
Transfer of energy from one place to another
Transverse waves
Particles vibrate at right angles to the waves direction of travel (propagation)
Longitudinal waves
Particles travel parallel to the wave direction of travel.
frequency and period definitions
frequency - Number of waves produced each second. Measured in Hertz (Hz)
period - Time taken for one whole wave to pass a point in space.
wave equation
V = f x λ
v = wave speed (m/s)
f = frequency (Hz)
λ = wavelength (m)
λ is pronounced ‘lambda’
forms of light
Light rays
Reflection of light
lane mirror
Refraction
is the bending of light as it travels between 2 different mediums with different refractive index.
n= Sinθx/ Sinθr
n = refractive index
θx = angle of incidence
θr = angle of refraction
Name the six ways in which you can describe an image
Enlarged / diminished
Inversed / upright
Virtual / real
How glasses work
we put lenses in the eyes to change the refraction.
Converging (concave) lenses help with long sight correction.
diverging (convex) lenses help with short sighted correction.
Total internal reflection
When a light ray travels from a medium of high refractive index to a medium of low refractive index it will refract away from the normal.
Critical angle
The incident angle that results in a 90 degree refraction is called the critical angle.
n = 1/Sinθc
n = refractive index
θc = critical angle
Properties of electromagnetic waves
transverse waves
Can travel through a vacuum (don’t rely on vibrations)
are vibrations
Travel very high speed in a vacuum
do electric fields have oscillating particles
no they have oscillating fields
wavelength (electromagnetic waves)
wide range of wavelengths and frequencies
direction (electromagnetic waves)
Direction of propagation of the wave; the direction the light travels. In a vacuum the speed of propagation is 3.0 x 10^8 m/s for all electromagnetic waves
magnetic field
There are two linked oscillating fields which are at right angles to each other and at right angles to the direction of propagation.
electromagnetic waves speed
3.0 x 10^8
same speed in air but slower in other materials eg in glass 2.5 x 10^8 m/s
Uses of the EM spectrum
Radio: communication (Radio a TV)
RFID tags (radio frequency identification)
Micro-waves: Heating food
cell phone signals
satellites
Infrared (IR): Heating
remote controls
Alarms
thermal imaging
Visible: sight
photograhy/film
illumination
Ultra-violet (UV): sterilisation
forgery detection
x-ray: Medical imaging
Security scanning. e.g) airports
Gamma: Quality control
imaging
cancer treatment
food sterilisation
Dangers of the EM spectrum
microwaves: heating of cells
Infrared: skin burns
UV: Damage cells, DNA, eyes
=> cancer or eyesight degradation
X-rays and Gamma:
Over exposure can cause DNA damage => mutation
General cell damage
List the EM spectrum in order of wavelength largest to smallest
Radiowaves largest
Micro-waves
infrared
visible
ultra-violet
x-ray
gamma frequency smallest
Sound waves
Are vibrations that allow energy to travel through a medium.
Speed of sound is higher in denser materials (name three examples and their speeds)
Air = 330-350 m/s
Water = 1500 m/s
Steel = 3100 m/s
what is the human hearing in hertz
20-20,000 Hz
Other uses of ultra sound
Sonar
Medical imaging of soft tissues
