P6 Waves Flashcards
What is amplitude?
The maximum displacement of a point on the wave from its undisturbed position
What is wavelength?
The distance between the same point on two adjacent waves
What is frequency?
The number of complete waves passing a certain point per second
What are transverse waves?
The oscillations are perpendicular to the direction of energy transfer
What are longitudinal waves?
The oscillations are parallel to the direction of energy transfer
What is specular reflection?
When a wave is reflected in a single direction by a smooth surface
What is diffuse reflection?
When the wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions
What happens when a wave crosses a boundary at an angle?
It changes direction and is refracted because its speed changes
What happens when a wave slows down at a boundary?
It will bend towards the normal
What happens when a wave speeds up at a boundary?
It will bend away from the normal
What happens when a wave travels along the normal?
It speed changes but it is not refracted
What happens to the wavelength and frequency of a wave when it is refracted?
The wavelength changes but the frequency stays the same
How are radio waves made?
- Alternating currents are made up of oscillating charges. As the charges oscillate, they produce oscillating electric and magnetic fields
- The object which charges oscillate to create the radio waves is called a transmitter
How are long-wave radio waves used for communication?
The long wavelengths bend around the curved surfaceof the earth for international communication
How are short-wave radio waves used for communication?
The short-wave wavelengths are reflected from the ionosphere into receivers
How do satellites use microwaves?
- A signal from the transmitter is transmitted into space
- It is picked up by the satellite receiver orbiting thousands of kilometres above the Earth
- The satellite transmits the signal back to earth in a different direction where it is received by a satellite dish on the ground
How do microwave ovens use microwaves?
The microwaves penetrate up to a few centimetres in the food before being absorbed and transferring the energy they are carrying to the water molecules in the food, causing the water to heat up and transfer this energy to the rest of the molecules in the food
How is temperature monitored using infrared radiation?
- Infrared radiation is given out by all hot objects. The hotter the object, the more IR radiation it gives out
- Infrared cameras can be used to detect infrared radiation and monitor temperature. The camera detects the IR radiation and turns it into an electrical signal, which is displayed on a screen
How do fibre optic cables use visible light?
Optical fibres are thin glass that can carry data over long distances as pulses of light. The light rays are bounced back and forth until they reach the end of the fibre
How are x-rays used in medicine?
The x-rays easily pass through flesh but not so easily through denser material like bones. The radiation absorbed gives you an x-ray image
What are black bodies?
A perfect blackbody is an object that absorbs all of the radiation that hits it. No radiation is reflected or transmitted
How do humans hear sound?
- Sound waves reach your eardrum, causing it to vibrate
- These vibrations are passed onto tiny bones in your ear called ossicles, through semi-circular canals and to the cochlea
- The cochlea turns these vibrations into electrical signals which get sent to your brain
What is the hearing range of humans?
20Hz-20,000Hz
What happens when an ultrasound wave passes from one medium to another?
Some of the wave is reflected off the boundary and some is transmitted
