P12 - Wave Properties✔️ Flashcards
Examples of mechanical waves?
-sound waves
-water waves
-sesmic waves
What is a mechanical wave?
Mechanical wave - wave that is an oscillation of matter and transfers energy through a medium(solid,liquid,gas)
Examples of electromagnetic wave?
-light waves
-radio waves
-microwave
-infra red
-visible light
-ulta violet
-x rays
-gamma rays
What is an electromagnetic wave?
Waves which can travel through a vacuum at the same speed of 300,000 km a second - no medium is needed
What type of waves are elecromagnetic?
Transverse waves - transfer energy from a source to an absorber
What is a transverse wave?
The oscillations of a transverse wave are perpendicular to the direction in which the waves transfer energy - most waves are transverse for example electromagnetic waves
What is a longitudinal wave?
-The oscillations of longitudinal wave are parallel to the direction in which the waves transfer energy
-they also show areas of compression and rarefaction
Sound and ultrasound waves are examples
What type of waves are mechanical?
Can be transverse of longitudinal
What happens when a sound wave passes through the air?
Sound waves travelling through the air are longitudinal waves - when object vibrates in air and makes the air around it vibrate as it pushes and pulls the air - these oscillations which travel through the air are sound waves
What type of waves are ripples on the surface of water?
Transverse waves
What is the amplitude of a wave?
The maxium displacment of a point on the wave from its undisturbed position
What is the wavelength?
The distance between the same point on two adjacent waves
What is frequency?
Frequency is the number of complete waves passing a certain point per second - measured in Hz - 1 Hz is 1 wave per second
What is a period?
The amount of time it takes for a full cycle of the wave
T = 1/f
Equation for period?
Period = 1 / frequency
T = 1/f
What is wave speed?
Speed at which energy is being transfered or speed of the wave traveling through the medium - equation is v = fλ
Wave speed equation?
Wave speed(m/s) = frequency(Hz) x wave length(m)
V = fλ
How do you measure sound waves in air?
1)attach a signal genarator to speaker - generate sounds with specific frequency use two microphones and an oscillosocpe to find wavelength
2)set up oscilloscope so detected waves at each mike are shown as seperate
3)start with both mikes next to speaker - slowly move one away until two waves aligned on display - but have moved exacty one wavelength apart
-measure distance between mikes - find wavelength
-use v = fλ to find wave speed
What happens when a wave is absorbed?
The waves are absorbed by the material they are crossing into - energy is transfered to the materials energy stores
What happens when a wave is transmitted?
The waves carry on travelling through the new material often leads to refraction
What are EM waves?
-All EM waves are transverse they transfer energy from a source to an absorber - they all travel at the same speed through air or vacuum
- they form a continous spectrum over a range of frequencies
Law of incidence?
Angle of incidence = ange of reflection
What is the angle of incidence?
The angle between the incoming wave and the normal
What is the angle of reflection?
The angle between the reflected wave and the normal
What is the normal?
The normal is an imaginary line that is perpendicular to the surface at the point of icidence ( point where wave hits the boundary)
Usually shown as a dotted line
What causes specular reflection?
Happens when a wave is reflected in a single direction by a smooth surface - eg when light is reflectd of a mirror
What causes a diffuse reflection? And what is it?
Diffuse reflection is when a wave is reflected by a rough surface eg piece of paper and the reflected rays are scattere in lots of different directions
What causes specular or a diffused reflection?
Caused when the normal is different for each incoming ray - which results in the angle of incidence being different for each ray - when light is reflected by rough surface the surface appears matte and you dont get a clear reflection
Can sound waves travel through solids?
Yes - sound waves can travel through solids causing vibrations in the solid
How do we hear sound waves?
Within the ears sound waves causes the ear drum and other parts to vibrate causes sensation of sound - humans have a restricted hearing range
Why do humans have limited hearing?
the conversion of sound waves to vibrations of solids works over a limited frequency range which restricts what humans can hear
Range arround 20Hz to 20kHz
Why is there such a large range of frequencys between EM waves?
EM waves are genarated by a variety of changes in atoms and their nuclei - eg changes in the nucleus creates gamma rays
Why can EM waves be used for different purposes?
Because EM waves have different properties making the usefull for differet purposes
What is refraction of waves?
When wave crosses boundary between material at an angle it changes direction its refracted
What determines how much a wave is refracted?
Determined by how much the wave speeds up or slows down - usually depends on the density of the two materials
-slows downs crossing a boundary it bends towards normal - speeds up into material it bends away from normal
Does frequency and wavelength change when a wave is refracted?
The wavelength of the wave changes when it is refracted but the frequency stays the same
If the wave is travelling along the normal - it changes speed but is not refracted
What is optical density?
Optical density of a material is a measure of how quickly light can travel through it - higher optical density slower light waves travel through it
Why can Em waves travel though a vaccum?
Em waves arent vibrations of particles they are vibrations of electric and magnetic fields allowing them to travel through a vacuum
What is echo sounding?
Using pulses of high frequency sound waves to detect objects in deep water and to measure water depth below hip
What is an echo?
An echo is the reflection of sound waves from a smooth surface
How does echo sounding work?
Pulse from transmitter reflected at the sea bed below ship and are detected by a reciever at the same depth as the transmitter - time taken for each wave is measured - equation the used to cacualte depth
What are ultrasounds?
Sound waves above the highest frequeny humans can detect are called ultrasound waves - humans can detect sound waves in range of 20 Hz to about 20kHz
What are ultrasound scanners used for?
Ultrasounds used for prental scans of a baby in the womb and getting images of organs in the body like kidneys and also muscles/ligaments
What do ultrasound scanners consit of?
made up of a transducer placed on the body surface - a control system - and a display system - transducer produces and detects pulses of ultrasound
What happens to ultrasound wave pulses from the transducer?
-Partially refleted from the different tissue boundaries in its path
-returns to the transducer as a sequence of ultrasound waves reflected by tissue boundaries arriving back at different times
How do ultrasound scanners work?
Transducer is moved across the surface of the body - ultrasound waves detected by transducer and build up image on screen of internal tissues
Advantages of ultrasound scanners?
-reflected at boundaries between different tissues types - used to scan organs and other soft tissues
-non ionising - radiation that does not have enough energy to remove an electron to ionise an atom - harmless
-used to destroy kidney stones
What is ionizing radiation?
Form of energy that acts by removing electrons from atoms and molecules - can travel unseen and pass through materials - can cause cancer - come with use of xrays
what are sesmic waves?
Energy transfered that travels through of across the earths surface
What is the focus of an earthquake?
The point at which the earthquake originates - nearest point on the centre is called the epicentre
What are P-waves or Primary waves
Cause the initial tremors lasting about one min - they are longitudinal that push or pull on material as they move through the eath
What are S-waves or secondary waves?
Cauase more tremors a few mins later they are transverse waves they shake material from side to side as they pass through the earth
What happens to P-waves at the boundary between the mantle and the outer core ?
They refract this is becuase of their abrupt change of speed at the boundary
Why cant S-waves travel through the liquid outer core?
They are tansverse waves so they cant travel through liquid outer core
How are sesmic waves prouced?
Produced in an earthquake and sread out from the epicentre
