Waves Flashcards
What happens when light hits a shiny surface?
It reflects.
When light being reflected is drawn what is the “i” and “r”
i = angle of incidence
r = angle of reflection
these are drawn between the ray and the normal
when light being reflected is drawn where is the “normal” drawn
The normal is drawn as a dashed at 90 degrees to the surface
State the law of reflection
Angle of incidence = angle of reflection
What are the three primary colours of light
red, blue and green
What is made when all three primary colours of light are mixed
they make white
What are the secondary colours of light
Magenta (red +blue)
Yellow (Red + green)
Cyan (Green +blue)
What happens when light moves from one material (medium) to another
the speed of the light changes
What happens when light travels from air to glass?
the light slows down and its wavelength decreases. on ray diagrams it moves towards the normal.
What happens when light moves from glass to air?
the speed of the light and the wavelength of the light increase. On ray diagrams it moves away from the normal.
What is the term for the change in speed of a wave when it moves from one material (medium) to another?
The change is speed is referred to as refraction
In addition to the change in speed what does refraction usually cause?
a change in direction of the wave
(This does not always happen)
When drawing a ray diagram the normal is …
drawn at 90 degrees to the surface where the ray enters the material
When drawing a ray diagram the angle of incidence is …
measured between the incident ray and the normal
When drawing a ray diagram the angle of refraction is…
measured between the refracted ray and the normal
What happens when all three primary colours mix together
they make white light
What are the two types of lenses
leses are one of the main uses of refraction
Convex
Concave
What are lenses used for
Used in glasses to correct vision
What is the order of the colours of light. In order of wavelength
Shortest, Refracts least
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Longest. Refracts most
What do waves transfer
Waves transfer energy
This could in the form of light energy, sound energy, heat energy or kinetic energy.
What is the crest/peak of a wave
The highest point of the wave
What is the trough of a wave
The lowest point of the wave
What is the amplitude of a wave
Half of the total height of the wave
What is wavelength
The wavelength of wave is the length of one wave.
Wavelength is measured in metres (m).
Wave length is given the symbol lambda λ
What are the two types of wave
Transverse wave
Longitudinal wave
What is a transverse wave
A transverse wave is one in which the vibrations occur at 90° to the direction of the wave.
What are some examples of a transverse wave
Water waves, light, all electromagnetic radiation
What is a longitudinal wave
A longitudinal wave is one in which the vibrations are in the same direction as the wave travel.
What is an example of a longitudinal wave
Sound waves
What is the frequency of a wave
Frequency of a wave is the number of waves per second.
What is the formula for frequence
f = N/t
where:
f = frequency measured in hertz (Hz)
N = number of waves
t = time measured in seconds (s)
What is the period of a wave
The period of a wave is the time taken for one wave to pass.
What is the formula for period of a wave
f = 1/T
Where:
f = frequence measured in hertz (Hz)
T = period of a wave measured in seconds (s)
How do you calculate wave speed
often waves can be treated as a regular object:
d = vt
where:
d = distance measured in metres (m)
v = speed measured in metres per second (ms^-1)
t = time measured in seconds (s)
however sometimes the wave equation has to be used:
v = f λ
where:
v = speed measured in metres per second (ms^-1)
f = frequency measured in hertz (Hz)
λ = wavelength measured in metres (m)
What is wave speed
The rate at which waves transfer energy from one place to another.
All EM waves travel at what speed?
Speed of light (3x10^8 ms^-1)
All waves can do what 3 things
Reflect
Refract
Defract
Describe diffraction
When a wave passes through a gap about the same size as its wavelength, it will spread out.
The same can happen if a wave passes around an objects.
This is known as diffraction.
(the spreading out of waves when they go through a gap, or past the edge of a barrier.)
What effects diffraction and how
Longer wavelengths diffract more than shorter wavelengths. Smaller gaps cause more diffraction than larger gaps.
How is sound made
In order for sounds to be made, something needs to be vibrating
What type of wave is sound
Longitudinal wave
(That means that the waves vibrate in the same direction as the wave travels. )
What can sound travel through
Sound needs particles to vibrate. This means it can travel through solids, liquids and gases, but not a vacuum.
What does the pitch of a sound depend on
The frequency of the wave
What does the volume of a sound depend on
The loudness of volume of a sound wave depends on its amplitude.
What is the speed of sound IN AIR
340 ms^-1
How does going through solids or liquids effect the speed of sound
The speed of sound is faster in solids and liquids than in gases like air because the particles are closer together.
Make a comparison between the speed of sound and light
The speed of light in air is 3 x 10^ 8 ms -1 (approximately 1 million times faster than sound), so we can assume that light reaches us instantaneously, whereas there is often a delay for sound.
What is the range of human hearing
The range of human hearing is between 20 Hz and 20 000 Hz. As you get older you range of hearing decreases.
What is infrasound
Sounds below 20Hz
What is ultrasound
Sounds above 20,000 Hz
How is ultrasound used in medicine
Ultrasound is used in hospitals to scan a baby in the womb. Ultrasound scans are safer to use than x-rays to produce an image of an unborn baby.
How do boats use ultrasound
Boats use SONAR that uses ultrasound to navigate underwater and to identify shoals of fish.
What are sound levels
The loudness of a sound is called the sound level and is measured in decibels (dB).
What sound levels are harmful and how is this prevented
Sounds over 85 dB can damage hearing so workers in very noisy places wear ear defenders or use noise cancelling headphones to protect their hearing.
What is used to measure sound levels
Sound meter
What is noise pollution
Noise pollution is defined as any unwanted noise.
What are some examples of noise pollution
traffic
construction
airports
classrooms of chatty pupils
How do noise cancelling headphones get rid of noise pollution
These headphones record the background noise and play it back through the headphones with the wave turned ‘upside down’ so that it cancels out the noise.
What is the Electromagnetic spectrum
The electromagnetic spectrum is a family of waves because they all travel at the same speed
List the parts of the EM spectrum in order of increasing frequency/ decreasing wavelength
Radio waves
Microwaves
Infrared
Visible light
Ultra violet
X rays
Gamma rays
All EM waves are what type of wave
Transverse wave
What is the rule for energy in the EM spectrum
The energy of the waves depends on their frequency.
The higher the frequency, the higher the energy.
What are common sources of Radio waves
Electronic circuits
Starlight
What are common sources of microwaves
Electronic circuits
Starlight
What are common sources of infrared
Warm objects
Sun
Electronic devices
What are common sources of visible light
Electronic devices (Ie LED)
Sun
What are common sources of Ultraviolet
Sun
What are common sources of x - rays
Some natural rocks
very fast electrons hitting a metal target
Man-made sources
What are common sources of gamma rays
Nuclear decay
Cosmic Rays
What can be used to detect radio waves
aerial
What can be used to detect microwaves
aerial
What can be used to detect infrared
black-bulb thermometer
electronic detectors (Thermistor, Ldr,Photodiode.
Phototransistor)
heat-sensitive papers
What can be used to detect visible light
eye, photographic film, electronic components (eg LDR)
What can be used to detect ultraviolet
causes fluorescence (glowing) in some objects,
film
What can be used to detect x rays
photographic film
What can be used to detect gamma rays
photographic film, GM tube
What are the typical uses of radio waves
communications, radio, TV
What are the typical uses of microwaves
communications satellites, telephony, heating water and food
What are the typical uses of infrared
detector in security lighting, remote controls (e.g. TV)
Thermal imagining camera
What are the typical uses of visible light
seeing, photography, communication (eg in optical fibres), laser surgery
What are the typical uses of ultraviolet
Detecting counterfeit bank notes, sun tanning lamps, killing bacteria.
What are the typical uses of X rays
imaging breaks/defects in bones, hidden devices
What are the typical uses of Gamma rays
medical tracers, killing cancerous cells, sterilisation of surgical equipment
