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39 Cards in this Set
- Front
- Back
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Name two types of waves |
Transverse or longitudinal |
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Give examples of transverse waves |
Water waves, gamma, x rays, ultraviolet, visible light, microwaves, radio waves |
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Give examples of longitudinal waves |
Sound |
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Define a transverse wave |
In a transverse wave the oscillation are at 90 degrees to the direction of energy |
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Define a longitudinal wave |
In longitudinal waves the oscillation are parallel to the direction of energy |
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What is a wave? |
A wave is an oscillation that transfers energy without transferring matter |
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Give two examples of how waves transfer energy without transferring matter |
1) ripples on a water surface cause floating objects eg twigs or birds move up and down but they don’t move across water 2) if you strum a guitar string and create sound waves, the sound waves don’t carry air away from the guitar to create a vacuum |
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Label a wave with the following: amplitude, wavelength |
Wave |
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Define amplitude |
Is the maximum displacement of a point on a wave from its undisturbed position |
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Define wavelength |
Distance between the same point on two adjacent waves |
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Define frequency |
Number of waves per second |
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What is the unit for frequency? |
Hertz (Hz) |
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Define period |
The amount of time it takes for one wave to pass a point |
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What is the unit for period? |
Seconds (s) |
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What is the equation that connects time period and frequency? |
Time period = 1 / frequency |
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What is the wave equation? |
Speed = frequency x wavelength |
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How can you measure the speed of sound in air? |
By using a signal generator and oscilloscope |
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How can you measure the speed of ripples on a water surface? |
Use a ripple tank |
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Define the words absorption, reflection and transmission |
Absorption - the light wave could be absorbed by the object, in which case its energy is converted to heat Reflection - reflected back Transmission - goes through |
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Explain how waves are reflected at a boundary |
Angle of incidence = angle of reflection |
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What is specular reflection? |
When parallel rays are reflected in a single direction eg by a smooth surface |
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What is diffuse reflection? |
When parallel waves are reflected by a rough surface and the reflected waves are scattered in lots of different directions |
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How do we hear? |
Sound waves cause the ear drum and other parts to vibrate which cause the sensation of sound. |
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What is the range of human hearing? |
20 Hz to 20 kHz |
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Define refraction |
The density of a material affects the speed that a wave will be transmitted though it. In general, the denser the transparent material is, the more slowly light travels though it |
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Explain what happens to light going from a less dense medium to a more dense medium |
Glass is denser than air, so a light ray passing from air into glass slows down. If the ray meets the boundary at an angle to the normal, it bends towards the normal |
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What is the speed of sound in air? |
A typical value is 330 m/s |
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Define ultrasound |
Have a frequency higher that the upper limit of hearing for humans ie above 20,000 Hz |
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What happens to ultrasound waves when they reach a boundary? |
They are particularly reflected when they meet a boundary between two different media’s. The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is. |
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Application for electromagnetic waves |
Radio - tv and radio Microwaves - cooking food Infrared - cameras, electrical heaters Visible light - fibre optic communications X-rays and gamma rays - medical imaging and treatments |
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How are seismic waves produced? |
Earthquakes |
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Describe p waves |
Are longitudinal, seismic waves. They travel at different speeds though solids and liquids. They are faster than S waves |
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Describe S waves |
Are transverse, seismic waves. Cannot travel though a liquid |
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How do s and p waves help us understand earth better? |
Provides new evidence about parts of earth which are not directly observable. Provide evidence for the structure and size of the earths core |
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Electromagnetic waves |
I |
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How to we transmit and detect radio waves? |
Can be produced by oscillations in electrical circuits. When they are absorbed they may create an alternating current with the same frequency as the radio wave itself |
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Where do gamma waves come from? |
From the change in the nucleus of an atom |
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Why are x-rays and gamma waves dangerous? |
Are ionising radiation that can cause the mutation of genes and cancer |
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What effects do x-rays and gamma rays have on the human body? |
The effects depend on the type of radiation and the size of the dose. |
