Electromagnetic waves Flashcards
What are electromagnetic radiations and how do they travel?
Electromagnetic radiations are electric and magnetic disturbances, they travel as waves and move energy from place to place.
Give one similarity shared by all electromagnetic waves and two differences.
All electromagnetic waves travel through space at the same speed, but they have different wavelengths and frequencies.
What are all the electromagnetic waves collectively known as?
The electromagnetic spectrum.
Describe the wavelength and frequency of gamma rays with regard to other waves in the electromagnetic spectrum.
Gamma rays have the shortest wavelength and highest frequency.
Describe the wavelength and frequency of radio waves with regard to other waves in the electromagnetic spectrum.
Radio waves have the longest wavelength and lowest frequency.
What is the relationship between the frequency of a wave and the amount of energy it transfers?
The higher the frequency of an electromagnetic wave the more energy it transfers.
At what speed do all electromagnetic waves travel through space?
300 million m/s
What equation links wave speed, frequency and wavelength?
v = f x lambda Where: v is the wave speed = 300 000 000 m/s f is the frequency in hertz, Hz Lambda is the wavelength in metres, m
What is visible light?
How does wavelength and colour vary across the spectrum?
What do we see a mixture of all the colours as?
Give one use of visible light.
Visible light is the part of the electromagnetic spectrum that is detected by our eyes, we see the different wavelengths within it as different colours.
Wavelength increases across the spectrum from violet to red.
White light
Photography
Give one application of Infrared radiation.
Remote controls for devices such as Tv’s and radios.
How are microwaves used in communications?
Microwave transmitters produce wavelengths that are able to pass through the atmosphere, they are used to send signals to and from satellites and within mobile phone networks.
How are radio waves used in communications?
Radio waves transmit radio and TV programs and carry mobile phone signals.
What affect can microwave radiation and radio waves have on the body?
Microwave radiation and radio waves penetrate your skin and are absorbed by body tissue, this can heat internal organs and may damage them.
What affect can infrared radiation have on the body?
Infrared radiation is absorbed by the skin: too much will burn your skin.
What happens when an alternating current is supplied to an aerial?
The aerial emits radio waves with the same frequency as the alternating voltage. When the waves are received they produce an alternating current in the aerial with the same frequency as the radiation received.
What is the radio and microwave spectrum split up into?
What are these used for?
The spectrums are divided into different bands
The different bands are used for different communication purposes.
What is the relationship between the wavelength of the waves and the amount of information they carry?
How does a wave with a short range behave?
The shorter the wavelengths of the waves the more information they carry.
The shorter a waves range, the less they spread out.
What part of the body and in which age group especially do scientists believe mobile phones may affect?
The brain and especially in children
What are optical fibres and for what are they used?
How do signals travel down the fibre?
Optical fibres are very thin glass fibres , we use them to transmit signals carried by visible light or infrared radiation.
By repeated total internal reflection
Why are optical fibres useful in communications?
They are useful in communications because they carry much more information and are more secure than radio wave and microwave transmissions.
What is the Doppler effect?
Give an example of the doppler effect demonstrated with sound waves.
If a wave source is moving relative to an observer, the wavelength and frequency of the waves detected by the observer shift from the original produced by the source.
An ambulance siren will sound different depending on whether it is moving away from you; pitch is lower. Or moving toward you pitch is higher.
What happens to the frequency and wavelength, when a source moves away from the observer?
The observed wavelength increases and the frequency decreases.
What happens to the frequency and wavelength, when a source moves towards the observer?
The observed wavelength decreases and the frequency increases.
What is a galaxy?
What is red-shift?
A large collection of stars.
Red-shift is where light observed from distant galaxies has been shifted to the red end of the spectrum, this means that the frequency has decreased and the wavelength increased.
