Waves Flashcards
WHAT ARE WAVES FOR
Waves transfer energy and carry signals.
WHAT IS A TRANSVERSE WAVE
Particle vibrations are perpendicular to the energy transfer. eg. electromagnetic radiation and water waves
Crest - highest point of the wave.
Trough - lowest point of the wave.
Amplitude - distance from the mean position to the crest or trough.
Wavelength - the distance from one part of the wave to the next where it begins to repeat itself.
Mean position - middle of the wave.
WHAT IS A LONGITUDINAL WAVE
Partial vibrations are in the same direction as the energy transfer.
Wavelength - Compression to compression, refraction to refraction.
Compression - where the particle are compressed.
Refraction - where the particle are spread out.
WHAT IS FREQUENCY
The number of waves to pass a point in one second (Hertz)
WHAT IS PERIOD
The time for a wave to travel one wavelength (seconds).
WHAT IS WAVESPEED
The distance travelled by a wave in 1 second (metres per second)
TRANSMISSION OF SOUND
For sound to be produced, an object must vibrate. Sound is carried from one place to another by vibrating particles. Sound can not travel through a vaccum as there is no particle, a solid, liquid or gas is required for sound to be transmitted.
EXPERIMENT TO MEASURE THE SPEED OF SOUND
- Produce a sound with a hammer.
- When the sound wave passes microphone A, it will start the clock on the electronic timer.
- When the sound wave reaches microphone B, the electronic timer will switch off.
- The distance between both microphones is measured.
- The distance is the measured in metres (must be atleast 1 metre) and is divided by the time on the timer.
WHAT IS THE RANGE OF HUMAN HEARING
20 - 20 000 Hz
ECHO SOUNDING
This is a type on sonar navigation to determine the depth of water by transmitting sound waves into the water. Then the time between emission and return is recorded and halved. Then the formula d=vt is used.
ULTRASOUND
Ultrasound is a high frequency sound (above the range of human hearing) used to monitor fetus’ and detect blood flow in heart, arteries and veins. A layer of jelly is placed between the transducer and skin to exclude all air and make good contact with the skin so that the waves don’t reflect. The waves reflect off of the fetus and build up an image of it.
WHAT IS DIFFRACTION
Diffraction is when a wave passes round a bend or through a gap and bends.
The amount of diffraction through a gap depends on the size of the gap or the wavelength. If the gap is the same width or smaller than the wavelength, the waves are circular.
Around an object, longer wavelengths diffract more than shorter wavelengths. Example: Some radio waves have a long enough wavelength to diffract over a hill and reach house aerials.
DESCRIPTION OF THE ELECTROMAGNETIC SPECTURM
They travel at the speed of light, they don’t need particles of matter in order to travel. The higher the frequency the greater the energy. They are all transverse waves. The frequency gets higher as it goes along.
ORDER OF THE ELECTROMAGNETIC SPECTRUM
Radio and TV, Microwave, Infra red, Visible light, Ultraviolet, X-rays, Gamma rays.
(RADIO AND TV) SOURCE, APPLICATION, DETECTORS AND POTENTIAL HAZARDS
Source: Electrical aerial, radio transmitter.
Application: Radio broadcasting, telecommunications.
Detectors: Aerial and reciever.
Potential hazards: Increased cancer risk
(MICROWAVE) SOURCE, APPLICATION, DETECTORS, POTENTIAL HAZARDS
Source: Magnetron inside a microwave, stars.
Application: heating food, radars in ship navigation, weather forecasting
Detectors: Aerial and receiver, diode probe.
Potential hazards: Heating of body tissues, cataracts in eyes.
(INFRARED) SOURCE, APPLICATION, DETECTORS AND POTENTIAL HAZARDS
Source: Lamps, flames, stars, remote controls.
Application: IR webcams, heat lamps (treating muscle injuries) thermograms.
Detectors - Photo transistor, LDR, Thermistor.
Potential hazards - heating of body tissues.
(VISIBLE LIGHT) SOURCE, APPLICATION, DETECTOR, POTENTIAL HAZARDS
Source: Anything that glows eg. bulbs.
Application: Vision, lasers.
Detectors: Retina in the eye, photographic film, LDR
Potential hazards: Damage to the retina if too much light.
(ULTRAVIOLET) SOURCE, APPLICATION, DETECTORS, POTENTIAL HAZARDS
Source: UV lamps, sunlight
Application: Checking security markings on bank notes, curing gel nail polish, treating some skin conditions.
Detectors: fluorescent paints and pens.
Potential hazards: can cause skin cancer, sunburn, damage to the retina.
(X-RAYS) SOURCE, APPLICATION, DETECTOR, POTENTIAL HAZARDS
Source: X-ray tube in a machine, cosmic sources.
Application: Medical imagery eg. detecting broken bones, checking weld quality in pipes.
Detectors: Photographic film.
Potential hazards: destroys cells which can lead to cancer.
(GAMMA RAYS) SOURCE, APPLICATION, DETECTORS, POTENTIAL HAZARDS
Source: Nuclear decay, stars, radioactive waste.
Application: Radiotherapy, tracers in body.
Detectors: Geiger-müller tube and counter, photographic film.
Potential hazards: damage to growing tissues, cell damage.
HOW DOES LIGHT TRAVEL
In straight lines
WHAT IS THE NORMAL
A reference line at 90^
WHAT IS THE INCIDENT RAY
The ray of light which hits the surface
WHAT IS THE ANGLE OF INCIDENCE
The angle between the ray of incidence and the normal.
WHAT IS THE REFLECTED RAY
The ray of light which comes off the mirror.
WHAT IS THE ANGLE OF REFLECTION
The angle between the normal and ray of reflection
WHAT IS THE LAW OF REFLECTION
Angle of incidence = angle of reflection
WHAT IS THE REVERS-ABILITY OF LIGHT
When light can be shone back along its path and come to its starting point
WHAT IS REFRACTION
When light travels into a material of different optical density and changes speed
WHAT IS THE LAW OF REFRACTION
Angle of incidence = angle of refraction
WHAT HAPPENS WHEN LIGHT TRAVELS FROM AIR TO GLASS
It slows down and its wavelength decreases. The frequency stays the same.
WHAT IS THE CRITICAL ANGLE
The critical angle is the angle of incidence when the angle of refraction is 90^
WHAT IS TOTAL INTERNAL REFLECTION
When the angle of incidence is greater than the critical angle.
WHAT IS A CONVEX LENS (CONVERGING)
Oval shape
Brings the light to a focal point. Corrects long sight. A thicker lens would bring the light to a focal point sooner and shortening the focal length.
WHAT IS A CONCAVE LENS
Weird shape
Rays of light are spread out, corrects short sight.
virtual focus is infront of shape because the rays spread out.
WHAT ARE LENSES USED IN
Cameras, telescopes, binoculars
