P6 Waves Flashcards
What is wavelength
The distance from a point on a wave to the equivalent point on. The adjacent one. Measured in meters
What is amplitude?
The maximum displacement of a point on a wave away from its undisturbed position.
What is frequency?
The number of complete waves that pass a point in 1 second.
Measured in Hertz
What is time period?
The time to complete one wavelength
What is a transverse wave?
Particles are at right angles to the direction of the energy transfer. Move up & down. Eg. Water waves
What is a longitudinal wave?
The vibrations of the particles are parallel to the direction of energy transfer. Move left & right
What is compression
Where the particles are closer together
What is rarefaction
When the particles are spread out.
Sound waves
They are longitudinal.
Change in speed of sound waves
When a sound is transmitted across a boundary from one medium to another, it’s speed changes.( frequency stays the same and wavelength changes)
Electromagnetic waves
Microwaves- transfers data to mobile phones
Electric fire- transfers infrared waves to heat us up
Ultraviolet- transferred from the sun
X-Ray machine -transfers X-rays which some of is absorbed by the body.
Radioactive sources- transfer gamma rays
What is an echo?
A reflected sound
Echo sounding
Animals can hear higher frequencies than us. Bats emit pulses of 20000Hz to 100000Hz.
Ships use high frequency sounds to find the depth of the seabed or to locate a shoal of fish.
What is the human sound range?
20Hz to 20KHz
Anything above 20KHz are considered ultrasounds
RP: measuring the wavelength and speed in a ripple tank and waves in a solid.
Use a ripple tank to measure/calculate wavelength and frequency then work out speed.
Use a mechanical vibrator to vibrate a stretched string. To produce a transverse wave. Once the wave is travelling at a steady speed count the wavelength and frequency then calumet the speed.
What is a ray diagram?
Model that shows the number of lines (rays) travelling in a straight line between the wave source and an object or surface. The arrow on the ray shows the direction it is traveling in.
Incident Ray is the one going to the surface and the rejection Ray is the one going away from the surface
What happens when a wave meets a boundary?
It is either reflected, absorbed or transmitted
Law of reflection
When a wave is reflected off a surface, the angle of incidence is equal to the angle of reflection
What is refraction
When a wave changes direction & speed when it enters a different medium.
RP: investigate the reflection of light by different types of surface and the refraction of light by different substances
Specular reflection- all light rays reflected at the same angle
Diffuse reflection- light from one direction is reflected at many different angles.
When light rays enter a denser material, it bends towards the normal.
The angle of reflection should be the same as the angle of refraction.
Speed of sound in different media
Solids are dense so sound travels the quickest in them as the particles are closely packed together.
Uses of ultrasound
Industrial- find cracks/ gaps in aircrafts & measure thickness of objects
Medical- body scans (babies in the womb), measure speed of blood flow in a vein or artery
Why do we use ultra sounds instead of X-rays
Safety- ultrasounds are safe, X-rays are ionising radiation
Imaging- X-rays have high penetrating power so travel through soft tissue, ultrasounds reflect off soft tissue to produce an image