P1.5 Waves Flashcards
What are waves?
Made up of many particles. Waves transfer energy from one place to another.
What are transverse waves? Give an example.
Waves that move up and down (perpendicular)
Like light or heat waves
What are longitudinal waves? Give an example.
Particles that move parallel to the direction of energy transfer.
Sound waves
What’s frequency?
The number of waves per second measured in Hertz (Hz)
What’s the top of a wave called?
Peak or crest
What’s the bottom of a wave called?
Trough
What’s the wavelength of a wave?
The distance from peak to peak or tough to trough.
What’s the speed of any electromagnetic wave?
3 X 10 to the 8 m/s
What’s the amplitude of a wave?
From the middle to the peak/trough of he wave
How do you calculate wave speed? Give the units.
Frequency X wavelength
Frequency - Hz
Wavelength - m
Wave speed - m/s
What’s the law of reflection?
The angle of incidence = the angle of reflection
What are the features of an image produced on a plane mirror?
The same size as the object
The same distance behind the mirror as the object is in front
Upright
Back-to-front compared with the object (lateral inversion)
Virtual
What are real images?
They’re formed where light rays cross after reflection by a mirror. They can be cast onto a screen.
What are virtual images?
They are formed where light rays only appear to come from. They can’t be cast onto a screen.
What is the relationship between the angle of incidence and the angle of refraction?
As the angle of incidence increases so does the angle of refraction. But as it increases the difference between the two angles increases.
What happens when light enters a more dense substance?
It slows down and bends towards the normal.
What happens when light enters a less dense substance?
It speeds up and bends away from the normal
What’s dispersion?
When a spectrum is formed. A prism splits the colours of white light into the spectrum. Red, orange, yellow, green, blue, indigo, violet.
Violet light refracts the most and red the least.
What’s diffraction?
The spreading of waves when they pass through a gap or move past an obstacle.
Most diffraction occurs when the gap width is similar to the wave-length of the wave.
In diffraction, what happens when the gap is too small?
The waves are reflected by the barrier
In diffraction, what happens when the gap is the same size as the wavelength?
Circular waves are produced
In diffraction what happens when the gap is bigger than the wavelength?
The waves pass through the gap unchanged apart from a slight diffraction of the waves near their ends.
What’s an example of diffraction in day-day life?
Radio waves diffract around the hills to reach houses. Sometimes they don’t diffract enough and this means the tv picture will be fuzzy.
What are sound waves?
Vibrations that travel through substances. It consists of a series of compressions and rarefactions.
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Compressions are where the particles are close together and rarefactions are where the particles are far apart.
