P12-Wave properties Flashcards
What are mechanical waves?
They are waves that are vibrations that travel through a substance e.g. sound, water
What are electromagnetic waves?
They are waves that can travel through a vacuum at 300,000 kilometres per second. These waves are always transverse .e.g. light and radio waves
What is a transverse wave?
It is a wave that oscillates perpendicular to the direction of energy transfer of the waves e.g. ripples on water and all electromagnetic waves.
What is a longitudinal wave?
The oscillations of a longitudinal wave are parallel to the direction in which the waves transfer energy e.g. sound waves, mechanical waves can be both transverse and longitudinal
What is the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position. The bigger the amplitude, the more energy the wave carries.
What is the wavelength?
The distance from a point on a wave to the equivalent point on the adjacent wave.
What is frequency of a wave?
It is the number of waves passing a fixed point every second.
What is the formula for a period?
Period(seconds)=1/frequency(Hz)
What is wave speed?
The distance travelled by each wave every second through a medium. Energy is transferred by the waves at this speed.
What is the formula for wave speed?
Wave speed(m/s)=frequency(Hz) x wavelength(metres)
How can you investigate reflection using a ripple tank?
Plane waves are produced by dipping an end of a ruler in water, directing it at a metal barrier. These waves are the incident waves and are reflected by the barrier.
How can you investigate refraction using a ripple tank?
Use a vibrating beam to create plane waves in a ripple tank containing a transparent plastic plate. Arrange the plate so the waves cross a boundary between the deep and shallow water. At a non-zero angle to a boundary the waves change their speed and direction when they cross the boundary. Perpendicular to a boundary however the waves cross the boundary with no change in direction but a change in speed.
What is refraction?
When plane waves cross a boundary at a non-zero angle to the boundary, each wavefront experiences a change in speed and direction. The refracted wave and the incident waves have the same frequency but they travel at different speeds so have different wavelengths.
What happens when a wave meets a boundary?
The wave can either be transmitted or absorbed but as they travel through, the amplitude of the waves decreases as the substance absorbs some of the waves energy.
What are sound waves?
It is a vibration that travels through a medium. They cannot travel through a vacuum however. Pitch increases with frequency and amplitude increases with loudness.
What is the speed of sound?
343 m/s
Why is human hearing limited?
It is due to the conversion of sound waves to the vibrations of solids only working over a limited frequency range so the frequency range of the human ear is limited.
What is echo sounding?
It is where ships use pulses of high-frequency sound waves to detect objects in deep water and to measure water depth below a ship.
What are ultrasound waves?
They are sound waves above the highest frequency that humans can detect. ( above 2kHz)
What is an ultrasound scanner?
It is made up of a transducer and a display screen. The transducer produces and detects sets of ultrasound waves. Each ultrasound wave pulse is partially reflected from some tissues and returns to the transducer as a sequence of ultrasound waves, arriving back at different times.
What are the advantages of ultrasound waves?
They can be used to scan organs and other soft tissues in the body as they are reflected at boundaries between different types of tissue. They are non-ionising so it is harmless when used for scanning.
What are seismic waves?
Waves that travel through the earth and across its crust.
What are the three different types of seismic waves?
1.Primary waves(P-waves) which cause the initial tremors
2.Secondary waves(S-waves) which cause more tremors a few minutes later
3.Long waves(L-waves) which arrive last and cause the more violent movements.
Where are the P and S waves in the earth’s structure?
The P and S waves bend as they travel through the mantle, the P waves refract at the boundary between the mantle and the outer core and the S waves are transverse waves so they can’t travel through the liquid outer core.
How can sound travel faster?
By travelling through a dense medium like a solid as sound needs particles to travel through.
What happens as a sound changes medium?
Frequency does not change, instead the wavelength gets longer as the sound speeds up and gets shorter when it slows down.
