Waves Flashcards
Order the electromagnetic waves from highest to lowest wave length
Radio waves Microwaves Infrared radiation Visible light Ultraviolet radiation X-rays Gama rays
What are the uses of UV rays?
1) killing bacteria (water purification)
2) security markings (checking banknotes)
3) fluorescent lamps (tanning machines)
4) data reading (blu-ray devices)
5) medical uses (setting dental fillings)
What are the uses of radio waves?
1) satellite transmissions
2) broadcasting TV and radio
What are the uses of microwaves?
1) cooking in microwaves
2) satellite transmissions (GPS)
3) communications via mobile phones
What are the uses of infrared?
1) cooking in ovens
2) thermal imaging (find people in collapsed buildings)
What are the uses of visible light?
1) transmissions via optical fibres
2) photography
3) form lasers which are used to read compact disks and bar codes
What are the uses of X-rays?
1) medical x-rays
2) airport security scanners
What are the uses of gama rays?
1) sterilise food and medical equipment
2) treating cancer (radiotherapy)
What are the dangers of UV rays?
1) sunburn
2) damage to surface cells (skin cancer)
3) blindness
What are the dangers of microwaves?
1) internal heating of body tissue leads to burns
2) cataracts
What are the dangers of infrared?
Skin burns
What are the dangers of gama rays?
1) kill cells
2) less to cell mutation (cancer)
What happens when light rays enter a more optically dense medium?
Bend towards the normal
As you move from gama rays to radio waves what happens?
1) wavelength increases
2) frequency decreases
What speed do wave sin the electromagnetic spectrum travel at?
3 x 10^8 m/s (speed of light)
What is meant by the term virtual image?
Rays do not actually come from there
Give an example of a wave that travels as a longitudinal wave
Sound waves
What is the difference between transverse and longitudinal waves?
1) the oscillations of a transverse wave are perpendicular to the direction of travel
2) the oscillations of a longitudinal wave are parallel to the direction of travel
What properties of electromagnetic waves makes microwaves suitable for communications with a satellite in space?
1) travel very fast (at the speed of light)
2) can travel in a vacuum
What are the similarities between all the electromagnetic waves?
1) same speed in a vacuum
2) transverse waves
3) can travel through a vacuum
4) carry information
5) transfer energy
What is the frequency range for human hearing?
20 Hz to 20,000 Hz
What is Snel’s law?
refractive index = sin(i) ÷ sin(r)
What is the angle of incidence?
The acute angle between the light ray and the normal
What is the angle of reflection?
The angle between the reflected light Ray and the normal
What is the angle of refraction?
The angle between the refracted light ray and the normal
What is the amplitude of a wave?
The maximum displacement from the equilibrium position
What is the frequency of a wave?
The number of complete cycles the wave makes in one second
What is the wavelength?
the distance between two points on a wave (e.g. two peaks)
What is the time period of a wave?
The time taken for 1 complete wave
What remains constant when a wave travels from one medium to the next?
The frequency
How is information transmitted along optical fibres?
1) light is totally internally reflected
2) because the angle of incidence is greater than the critical angle
What is the critical angle?
The angle above which total internal reflection begins
How do you measure the speed of sound in air?
1) connection two microphones to an electric clock
2) place the microphones 1 m apart
3) use buzzer to make a loud sound in still air
4) when sound reaches first microphone the timer starts and when it reaches the second microphone timer stops
5) calculate speed of sound in air using formula: speed = distance ÷ time
6) repeat and average
What is meant by the term total internal reflection?
1) reflection from a surface inside the material
2) all of the light is reflected
3) reflection occurs inside the optically more dense medium
4) light incident at angle greater than critical angle
What are the uses of total internal reflection?
1) in endoscopes
2) in optical fibres for communication
3) rectifying prison in binoculars
What is a similarity between a transverse wave and a longitudinal wave?
Both transfer energy
What is meant by the term refraction?
Change of direction of a wave (as it changes from 1 medium to another)
Which colour of light is refracted the least?
Red light (as has longest wavelength in visible light)
What do waves transfer?
Energy (NOT matter)
What is ultrasound?
Sound waves with frequencies above human hearing
What are the applications of ultrasound?
1) echo sounding (calculate distance)
2) ultra sound (check babies in womb)
3) motion sensors (study movement)
What pieces of equipment do you need in order to display a sound wave?
1) oscilloscope
2) microphone
Describe how a student would use a oscilloscope and microphone to determine the frequency of sound
1) adjust oscilloscope to get a steady trace
2) adjust time base to give a minimum of 1 complete cycle on screen
3) measure the number of squares for a number of complete cycles of waves
4) multiply the number of squares by the time base to find the time period
5) use f = 1 ÷ t
What happens to waves as they pass through a gap?
They are diffracted (NOT defracted)
What does not change as a wave is diffracted?
The wavelength
What affects the extent to which a wave is diffracted?
The size of the gap compared to the wavelength (smaller gap=larger diffraction)
What kind of waves experience diffraction?
Transverse waves (that includes light waves) and longitudinal waves (including sound waves)
What is an analogue signal?
One that has a wide range of continuously varying levels
What is a digital signal?
A signal that has only two values as it represents a binary number (a number containing only 1s and 0s)
What are the advantages of using digital signals rather than analogue signals?
1) digital signals are less prone to interference so quality can be maintained over longer distances
2) digital signals carry more information per second
3) can be regenerated (able to boost signal to original strength)
How can digital signals carry more information than analogue signals?
The can be compressed to increase their bandwidth
What do the x and y axis on an oscilloscope represent?
X = time Y = amplitude
What does the pitch of a sound depend on?
The frequency of vibration of the source
What does the loudness of a wave depend on?
The amplitude of the vibration
How does a graph show a signal is digital?
It has only two values
How can a digital signal be made to carry more information?
1) increase the bit rate/frequency
2) use an additional signal level
3) increase bandwidth
4) multiplex (use more than one channel)
What is meant by the term pitch of a sound?
1) the frequency of a wave
2) high sound has high frequency
suggest why the diffraction of microwaves can not be seen but with radio waves it can as they pass through the same sized gap
1) microwaves not diffracted as much
2) diffraction only seen when size of barrier/gap
is comparable to wavelength
3) radio-waves have much longer wavelength than microwaves
explain how the wave pattern that is produces when a wave moves through a gap occurs
1) diffraction
2) the incoming wave spreads out at the gap OR the energy carried by the wave spreads out
explain why light waves do not make a similar pattern to water waves when they travel through the same gap
1) diffraction only apparent when the wavelength and the size of the gap are comparable
1) wavelength of light is very small/smaller than water waves smaller than the gap
explain how a decrease in temperature affects the wavelength of sound waves
1) speed of sound decreases with temperature
2) frequency is constant
3) so wavelength decreases with temperature
use ideas about diffraction to explain why different frequencies of sound waves require different sizes of louspeaker
1) Waves spread out as they leave the speaker
2) Different frequencies different wavelengths
3) Diffract most if speaker size matches wavelength
4) Giving a more even sound if all frequencies diffract equally
