Chapter 12 Wave Properties Flashcards
12.1 What are waves?
They can be used to transfer energy and information.
12.1 What are mechanical waves?
These waves need a medium to travel through. They can be transverse or longitudinal waves.
Examples are: sound waves, water waves and seismic waves.
12.1 What are transverse waves?
Transverse waves oscillate perpendicular to the direction of energy transfer of the waves. Ripples on the surface of water are transverse waves. So are all electromagnetic waves.
12.1 What are longitudinal waves?
Longitudinal waves oscillate parallel to the parallel to the direction of energy transfer of the waves. Sound waves in air are longitudinal waves.
12.1 What are electromagnetic waves?
Waves that can pass through a vacuum and no medium is needed.
12.2 What is the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position. On a diagram, it is the displacement from the middle to the peak.
12.2 What happens to the energy when the amplitude increases?
The bigger the amplitude of the waves, the more energy the waves carry.
12.2 What is the wavelength?
The wavelength of a wave is the distance from a point on the wave to the equivalent point on the adjacent wave. It is from one peak (the top of the wave) to another or from one trough (the bottom of the wave) to another.
12.2 What is the frequency of a wave?
The number of waves passing a fixed point every second is called the frequency of the waves.
12.2 What is the period of a wave? And equation
The period of a wave is the time taken for each wave to pass a fixed point.
Period (seconds) = 1/frequency (hertz)
12.2 What is the speed of a wave?
The speed of the wave is the distance travelled by each every second through a medium.
12.2 What is the wave speed equation in terms of frequency x wavelength
Wave speed = frequency x wavelength
12.3 How can reflection be understood by the ripple tank?
Plane waves in a ripple tank are reflected from a straight barrier at the same angle to the barrier as the incident waves because their speed and wavelength do not change on reflection.
12.3 What does refraction mean?
Refraction of waves is the change of the direction in which they are travelling when they cross a boundary between one medium and another medium.
12.3 How can refraction be shown?
Plane waves crossing a boundary between two different materials are refracted unless they cross the boundary at normal incidence.
12.3 What happens at a boundary?
Waves can transmitted or absorbed.
12.4 What are sound waves?
Sound waves are vibrations that travel through a medium
12.4 What can sound waves not do?
They cannot travel through a vacuum
12.4 How can you investigate sound waves?
- A ripple tank for water waves
- A stretched spring for waves in a solid
- A signal generator and a loudspeaker for sound waves.
12.5 What happens when you increase the pitch of a note?
The pitch of a note increases if the frequency of the spund waves increases
12.5 How is the loudness of a sound wave increases?
The loudness of anote increases if the amplitude of the sound waves increases
12.5 How do sound waves make humans hear things?
Sound waves cause the ear drum to vibrate, and the vibrations send signals to the brain.
12.5 Why is human hearing limited?
The conversion of sound waves to vibrations of solids only works over a limited frequency range, so human hearing is limited.
12.6 What are ultrasound waves?
They are sound waves of frequency above 20kHz
12.6 How are ultrasound waves partly reflected?
They are partly reflected at a boundary between two different types of body tissue.
12.6 How can tou calculate the distance of ultrasound waves?
They are reflected at boundaries and are timed, the timings are used to calculate distances.
12.6 Why are ultrasound waves safer than X-rays?
They are non-ionising so it is safer than an x-ray
12.6 Distrance travelled by a wave (ultrasound)
Distance travelled by the wave (m) = speed of ultrasound waves in body tissue (m/s) x time taken (s)
12.6 The depth of the boundary below the surface for ultrasound waves equation
1/2 x speed of the ultrasound wave x time taken
12.7 What are seismic waves
Waves that travel through the Earth
12.7 How are seismic waves produced?
They are produced in an eathquake and spread out the epicentre
12.7 What are primary waves?
These cause tremors lasting about one minute. These are longitudinal waves that push or pull on materials as they move through the Earth
12.7 What are secondary waves?
They cause tremors a few minutes later. They are transverse waves that travel slower than P-waves. They shake the material that they pass through inside the Earth from side to side.
12.7 What are L-waves
Most violent move,ents are caused by this and they usually arrive last. They travel slower but occur in the crust.
12.7 What is the structure of Earth?
Solid inner core
Surrounded by a liquid outer core
Which is surrounded by the Earth’s mantle
The mantle is surrounded by the Earth’s crust
