Chapter 4&5 mock Flashcards
Formula triangle for wave length
V
F Y
(Upside down y = wave length)
Formula triangle for speed
D
S T
What do waves transfer
Energy and information
What is ultra sound
Give example
Greater than 20,000 hertz, used for scanning birth defects and manufacturing equipment
What is infrasound
Give example
Less than 20 hertz and is used to track animals or monitor seismic activity
What happens to waves in denser materials
They speed up and bend away from normal
What happens to waves in less dense materials
Slows down and bends towards normal
Name 3 characteristics of a primary wave
Fast
Compressional
Longitudinal
Name 2 characteristics of a secondary wave
Transverse
Slower
What can p waves travel through
Solids
Liquids
Gasses
What can S waves travel through
Solids only
What are sonar waves
Sonar waves are sound waves used for us to be able to “see” In water. They are waves making use of echos, the sound waves are sent off to the environment around it where the waves bounce off objects, when this happens they reflect it back.
What can the human ear hear
20-20K hertz
Why do they put a gel on the mums tummy before ultra sound scans
Allows scanner to move around and it acts as a medium for the waves to reflect into, more sound will be transmitted.
What waves are released after an earth quake
Seismic waves, p then s
What do waves transfer
Energy and information
Not matter
What is the wavelength of a wave
The distance between a point on one wage and the same point on the next wave- often easiest to measure from Crest to crest
What is the amplitude of a wave
It’s maximum disturbance from its undisturbed position
What is the frequency of a wave
The number of waves produced by a source each second or the number of waves that pass a certain point each second
Measured In hertz
What is the period of a wave
The time it takes to for one complete cycle of vibration to pass a given point
Difference between a longitudinal wave and a transverse wave
In longitudinal waves the oscillations are along the same direction as the direction of travel and energy transfer
Whereas in transverse waves the oscillations (vibrations) are at right angles to the direction of travel and energy transfer
Example of longitudinal waves
Sound waves
P waves
Examples of transverse waves
S waves
Water
Light and all other type of electromagnetic radiation
Formula for wave speed
Frequency x wavelength
What is refraction
When a wave change speed as it passes through a boundary between two substances with different densities such as air and glass. This causes them to change direction- this is called refraction.
What would cause refraction not to happen
If it crossed the boundary at an angle of 90* this is called the normal- in this case, they carry straight on.
What are som is of the effects that are a result from refraction
A swimming pool looking shallower than it actually is, bc the light coming from the bottom of the pool bends when it comes out of the surface due to refraction of light.
Twinkling stars due to refraction of light
A pencil partly in water appears bent at the surface of water, because the light coming from the stick bends when it comes out of the surface due to refraction of light.
What is the law of reflection
The angle of incidence equals the angle of reflection
E.g.- a wave hits a mirror at an angle of 36, it will be reflected at the same angle 36
Examples of reflection
Light reflecting off a mirror
Scenery being reflected off a smooth water surface
Seeing yourself in the mirror
Examples of waves being transmitted
Infrared light - tv remotes and can get converted into optical fibres-
Which are used to carry signals, computer data and telephone calls
Microwaves - transmit signals for mobile phone calls
Radiowaves- transmit television and radio programs as they reflect off a charged layer in the atmosphere
Examples of waves being absorbed
Light being absorbed in the colour spectrum eg- A blue object absorbs all the colours of the spectrum except blue- it reflects blue
A magenta object object absorbs all the other colours and reflects red and blue
Normal hearing range for humans
20hz to 20,000z
What are frequencies greater than 20hz called
Ultrasound
How is ultrasound used in sonar
A pulse of ultrasound is send out from ship and it bounces off the sea bed or any other objects and an echo is detected. The time it takes for these waves to travel backup indicates that depth of sea bed or object
.
Uses of ultrasound in body scanning
Checking condition of foetus
Investigating liver or heart problems
Breaking down kidney stones
Measuring blood flow in body
Explain how ultra sound is used in Foetal scanning
Ultrasound energy being reflected onto a screen to create a picture each time it passes from one material to another
What are sound with frequencies less that 20hz known as
Infrasound
Uses of infra sound
Elephants and giraffes communicate between herds over long distances, scientists use Microphones to track the herds even if hidden in dense forests
Used to detect volcanic eruption
Track meteors through atmosphere
What are some seismic waves
Infrasound waves
