P1.5 Waves Flashcards
What are the 2 types of wave?
Transverse or Longitudinal
Describe the oscillations in transverse waves
In transverse waves the oscillations are perpendicular to the direction of energy transfer
Describe the oscillations in longitudinal waves
In longitudinal waves the oscillations are parallel to the direction of energy transfer
What type of waves are electromagnetic waves?
transverse
What type of waves are longitudinal?
sound waves
Give some examples of mechanical waves
water waves, shock waves, waves on a rope
What type of wave are mechanical waves?
transverse or longitudinal
All types of electromagnetic waves travel at the ——– speed through a vacuume.
SAME
What sizes do wavelengths in the electromagnetic spectrum vary from?
about 10 to the -15 to more than 104 meters
What is the order of waves in the electromagnet spectrum, from long wave length to short wave length?
radio waves- Long wave length
microwaves
infrared waves
visible light
ultraviolet
Xrays
Gamma rays
What do longitudinal waves show areas of?
Compression and rarefaction
When do you see a clear reflection in the mirror?
When light travelling in the same direction reflects from an even surface so it is all reflected at the same angle
What is the law of reflection?
Angle of incidence = Angle of reflection
What is the normal?
A construction line perpendicular to the reflecting surface at the point of incidence
What is diffraction?
When waves bend round obstacles causing the waves to spread out.
What does the amount of detraction depend on?
the size of the gap relative to the wavelength of the wave
When does significant diffraction only occur?
When the wavelength of the wave is of the same order of magnitude (same size) as the size of the gap or obstacle.
Why is light hard to diffract?
As it has a vey small wavelength so needs a very small gap.
What is refraction?
When waves go through a new material, causing them to change direction
In refraction, when are waves not refracted ?
if waves travel along the normal.
To be refracted they need to meet the medium at an angle
What is the amplitude of a wave?
the displacement from the rest position to the crest.
What is the wavelength of a wave
The length of the full cycle of the wave
eg- from crest to crest
What is the frequency of a wave?
The number of complete waves passing a point per second
OR
The number of waves produced by a source each second
What do waves transfer?
energy
in the equation: speed= frequency x wavelength (v= f x y)
What are the units?
v , speed- m/s
f , frequency- Hz
y, wavelength- m
Describe the uses of radio waves
COMMUNICATION
- Long wave length means the wave diffracts around the curved surface of the earth and around hills and into tunnels.
- Used for TV and FM radio
Describe the uses of microwaves
SATELLITE COMMUNICATION and MOBILE PHONES
-Pass easily through atmosphere
What are some possible risks with mobile phones?
mobile uses microwaves to pick up signals.
Some wavelengths in microwaves are absorbed by water molecules and heat them up. If the water happens to be in your cells, they may become damaged.
What are some uses of infrared rays?
REMOTE CONTROLS and OPTIC FIBRES
-Remotes controls work by emitting different patterns of infrared rays to send different commands to an appliance.
What 2 rays are used in optical fibres?
infrared and visible light.
signal is carried as pulses of light of infrared radiation and is reflected off the sides of a very narrow core from one end of the fibre to another.
Describe some uses of visible light
PHOTOGRAPHY
What causes sound?
soundwaves, causing vibrations in a medium
Describe the speed of sound in different materils
fastest in solids
can not travel in a vacuum as there are no particles
What is the pitch of a sound determined by?
its frequency (higher the frequency, higher the pitch)
What is the loudness of a sound determined by?
its amplitude (the bigger the amplitude, the louder the sound)
What are echoes?
reflections of sounds
Describe the Doppler effect
When a wave source (light, sound or microwaves) moves away from an observer, the observed wavelength increases and the frequency decreases- lower pitch
When the source moves towards an observer, the observed wavelength decreases and the frequency increases.- higher pitch
What is the Doppler effect?
If a wave source is moving relative to an observer, there will be a change in the observed wavelength and frequency
Describe the theory of red shift and how it supports the Big Bang theory
- Red shift shows galaxies are moving away.
- More distant galaxies show a greater increase in wavelength so therefore a bigger redshift
- More distant galaxies are moving away faster
- This suggests that there was once a single point of origin
What is the Big Bang theory?
That the universe began from a very small initial point
What does CMBR stand for?
Cosmic Microwave Background Radiation
What is CMBR?
a form of electromagnetic radiation which fills the universe. It comes from radiation that was present shortly after the beginning of the universe - now seen as microwave radiation
How does the discovery of CMBR support the Big Bang theory?
The Big Bang theory is currently the only theory that can explain the existence of CMBR.
What are some limitations with the Big Bang theory?
- Some people still believe in other theories (steady state theory)
- There are observations the theory can not explain
- Does not explain what caused the explosion
What are some properties that are the same for both radio and microwaves?
can be used for communication
travel at the same speed through a vacuum and air
transverse waves
can be reflected/diffracted/refracted/absorbed
transfer energy
What is the property of microwaves that allows them to be used for satellite communications?
they can pass easily through the ionosphere
What do scientists believe is the origin of CMBR?
the Big Bang
How is the wave length of CMBR likely to change over the next billion years, why?
it is likely to increase
because the universe continues to accelerate outwards (expand)
What type of image is formed when you see an objects reflection in a mirror?
Virtual
Upright
Laterally inverted
Why is an image of a reflection virtual?
As the image is formed by virtual (imaginary) rays crossing
What is a virtual image?
it cannot be formed on a screen
What does it mean if the image formed in a mirror is laterally inverted?
left of the object seems to be on the right in the reflection
How many Hz are in a KHz?
1000
What happens when a metal arial absorbs radio waves?
an alternating current is created
with the same frequency as the radiowaves
the arial gets hotter
Why would an xray telescope based on earth not be able to detect xrays emitted from distant stars?
As xrays cannot penetrate the atmosphere
When considering the origin of the universe, what is difference between the ‘big bang theory’ and the ‘steady state’ theory?
Big bang theory- universe started at one point
Steady state theory- universe has no origin as it has always existed
Why does red-shift provide evidence to support both the big bang theory and the steady state theory?
Red shift provides evidence that the universe is expanding
both theories use the idea that the universe is expanding
Why are scientists keen to carry out research on theories about how the universe began?
to find evidence to support one or both of the theories
or
to find evidence to disprove one or both theories
Why do scientists not know why the universe was created?
insufficient evidence
Which type of electromagnetic wave has the shortest wave length?
Gamma
State differences between an ultraviolet wave and a visible light wave
Ultraviolet has a higher frequency
Ultraviolet has a greater energy
Ultraviolet has a shorter wavelength
What does red shift tell scientists about the direction most galaxies are moving?
away (from each other)
What information can scientists find out about a galaxy when they measure the size of the red shift the galaxy produces?
The distance (from earth)
The speed the galaxy is moving
What does the observation of redshift suggest is happening to the universe?
The universe is expanding
Give examples of infrared waves being used for communication
remote controls
optical fibres
Many scientists think that the Big Bang theory describes the….
origin of the universe
The discovery of cosmic microwave background radiation was important as it….
provided more evidence to support the big bang theory
What is is used to describe the wavelength of a planet or star moving closer to earth
blueshift
What is the electromagnetic spectrum?
Electromagnetic radiations which cover a continuous range of wavelengths
Explain why low emission mobile phones should be marked
allows people to easily identify lower risk phones
this allows people to make a more informed choice
Which part of the electromagnetic spectrum provides energy to heat water?
infrared
