3. Waves Flashcards
(24 cards)
Relate the pitch of a sound to the frequency of vibration of the source
The more something vibrates the higher frequency.
The higher frequency the higher pitch.
So the more vibrations the higher pitch.
Relate the loudness of a sound to the amplitude of vibration
The bigger the vibration the higher the amplitude.
The higher the amplitude the louder the sound.
Describe an experiment using an oscilloscope to determine the frequency of a sound wave
Have an noise made into a microphone attached to an oscilloscope, for example have someone try to sing a note. See how many oscillations there are per second, this will be your frequency. Try changing the pitch of the note and see it the number of oscillations per second changes.
An oscillation is the completion of one wave i.e from one peak and the next.
How can an oscilloscope and microphone be used to display a sound wave?
A microphone detects sound waves, it can feed this information into an oscilloscope which will display it as a wave (or straight line.)
What is the frequency range for human hearing?
20Hz - 20,000Hz
What types of waves are sound waves? (Longitudinal or transverse)
What can be done to them?
Sound waves are longitudinal waves.
They can be reflected, refracted and diffracted much like light can.
For example an echo is a reflection of sound.
Describe the advantages of using digital signals rather than analogue signals
The term noise means the random signals picked up by waves. Radios may crackle or internet may looses connection. This effects analogue signals badly as each time it is amplified the noise also gets amplified, this alters the signal making it hard or impossible to identify as the original signal.
In digital signals any noise picked up is likely to be of a smaller amplitude than that if the on state, this means something receiving it will ignore the noise as it is neither on nor off, this makes them less likely to be distorted.
What is the difference between analogue and digital signals?
Analogue : the amplitude and/or frequency constantly vary.
Digital : consists of pulses with two states ( on/off)
What is the relationship between critical angle and refractive index?
Sin (critical angle) = 1/ refractive index
Explain the meaning of ‘critical angle’
When light travels from one medium to another it is refracted; it changes angle due to change in density.
Past a certain angle the light will simply be refracted back into the medium it is in, this angle is the critical angle.
describe the role of total internal reflection in transmitting information along optical fibres and in prisms
Beyond the critical angle, light will be reflected back into the medium they came from at the same angle. In this way they are trapped in the medium.
By reflecting light past its critical angle you can make it travel through a medium to send information: this is done in optical fibres.
describe an experiment to determine the refractive index of glass, using a glass block
Shine a ray of light through a glass block, measure the angle of incidence and the angle of refraction. Do sin(i) ( angle of incidence ) divided by sin(r) (angle of reflection ) and you will have the refractive index of glass.
What is the relationship between refractive index, angle of incidence, and angle of refraction?
Refractive index= sin (angle of incidence)/ sin (angle of reflection)
n= sin(i)/ sin(r)
describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms
Place a block of glass on a piece of paper, drawing an outline.
At one point, draw the normal line.
Draw a line at 30 degrees to the normal line, shine a ray of light down this line.
Draw a line where the light comes out the other side. Connect the two lines, drawing the refracted ray.
Measure the angle of the emergent ray.
Repeat for different shaped glass.
What is the law of reflection?
The law of reflection is that the angle of incidence= the angle of reflection. (Always)
The angle of incidence is the angle that light hits a mirror; it is taken between 90 degrees from the mirror and the incidence wave (the wave that hits the mirror.)
The angle of reflection is the angle that light leaves the mirror; it is taken between 90 degrees from the mirror and the angle of reflection.
What type of waves are light waves? ( transverse/ longitudinal)
What can be done to them?
Light waves are transverse.
Reflection :
Light hitting a reflective surface will ‘bounce’ back from the surface (at the same angle they hit the surface.)
Refraction:
Light waves change speed when they pass through objects of different densities, this causes them to change direction. When they return to the original density they will continue in the original direction.
Diffraction:
When light meats a barrier, it will carry on through the gap and spread out in the area beyond.
What are the detrimental effects of excessive exposure of the human body to electromagnetic waves?
Microwaves
Infrared
Ultraviolet
Gamma rays
-microwaves: internal heating of body tissue
this can damage cells if they overheat
-infra-red: skin burns
skin cells are damaged by overexposure
-ultraviolet: damage to surface cells and blindness
can damage receptor cells in the retina
-gamma rays: cancer, mutation
can cause cells to change their arrangement causing cancer
What are some of the uses of electromagnetic radiations?
Radio waves? Microwaves? Infrared? Visible light? Ultraviolet? X-rays? Gamma rays?
-radio waves: broadcasting and communications
Vibrations carry sound
-microwaves: cooking and satellite transmissions
Vibrations create heat.
-infra-red: heaters and night vision equipment
Vibrations create heat, cameras can detect where it is high and low to see by heat.
-visible light: optical fibres and photography
Light reflected down tube to send signals, or onto film to take photos.
-ultraviolet: fluorescent lamps
A coating inside the bulb will absorb UV light and re-emit it as visable light.
-x-rays: observing the internal structure of objects and materials and medical applications
They pass through skin and soft tissue but reflect hard structures like bone.
-gamma rays: sterilising food and medical equipment
What is the electromagnetic spectrum?
The electromagnetic spectrum is a range of different frequency waves. All of the waves in the electromagnetic spectrum travel at the same speed when they are in a vacuum.
What is the equation linking wave speed, frequency, and wave length?
(Equation can be used for all types of waves)
Wave speed= frequency x wavelength
OR
Frequency = 1/ time period
Complete: Waves transfer…. And …. Without transferring…
Waves transfer energy and information without transferring matter.
define:
- amplitude
- frequency
- wavelength
- period of a wave
Period of a wave:
Time taken for the source to produce one complete wave.
Amplitude:
As a wave vibrates to either side of the direction of travel, the amplitude is the distance between the line of the direction of travel and the furthest point the it vibrates away from the line:
Frequency:
The number of waves per second, it is measured in Hertz (Hz). You can think of it as how quickly the waves are travelling.
Wavelength:
The distance between one point on a wave and the same point on the next wave; usually the point from the top/bottom of one wave (peak/trough) to the top/bottom of the next.
What are the differences between transverse and longitudinal waves?
What are some experiments to show longitudinal and transverse waves? (E.g. Ropes, springs, and water)
Transverse:
Vibrations (osculations) go up and down along the line of travel, (90 degrees to direction of travel)
Light and electromagnetic waves travel in this way,
If you drop something in water the waves move up and down as they travel outwards,
If you lie a piece of string on a table and move one end up and down, the movement will pass through the object to the other end.
Longitudinal:
The vibrations are in the same direction as the line of travel,
Sound waves travel in this way,
Compressions are where vibrations are close together, refractions are where they are more spread out,
If you push one end of a stretched spring the compression will move down the spring.
units:
degree (o) - hertz (Hz) - metre (m) - metre/second (m/s) - second (s) -
degree (°)- distance hertz (Hz)- cycles per second metre (m)- distance metre/second (m/s)- speed second (s)- time
