Topic 5- Light And The Electromagnetic Spectrum Flashcards
What are electromagnetic waves ?
All electromagnetic waves are transverse waves that travel at the same speed (velocity) in a vacuum
How many waves can the electromagnetic spectrum be split into ?
The electromagnetic spectrum is continuous but can be split into seven types of wave.
Order the electromagnetic spectrum in highest frequency to lowest frequency ?
In order of highest frequency to lowest the seven types are:
gamma X-ray ultraviolet (UV) visible infrared microwave radio waves
How do electromagnet waves transfer energy ?
Electromagnetic waves transfer energy from a source to an observer or object.
What wave carry’s more energy then any other type of wave on the EM spectrum?
Gamma rays carry more energy than any other wave in the electromagnetic spectrum.
How do gamma rays transfer energy to our skin ?
They may transfer energy from one source to our skin if we come into contact with gamma rays
As you Kiev from gamma rays to radio waves what happen to the wavelengths and frequencies ?
As you move from gamma rays to radio waves, the wavelengths increase and the frequencies decrease.
What wave has the shortest wavelength and the highest frequency ?
Gamma rays
What wave has the longest wavelength and the lowest frequency ?
Radio waves
What wave in the EM spectrum carry’s the most amount of energy ?
Gamma rays
Why are electromagnetic waves with higher frequencies usually more dangerous ?
Because of their energy
What are the uses of gamma rays ?
medical imaging and therapy, astronomy, sterilisation and food preservation
What are the risks of Gamma rays ?
They are extremely penetrating and damaging to living tissues and cells
Why can be use gamma rays to destroy bacteria and tumours ?
Because they carry the most energy
As wavelength of a wave increases, what happens to its frequency ?
It decreases
Which type of electromagnetic wave has the lowest frequency?
Radio waves
What waves carry the second most energy of all the waves in the electromagnetic spectrum ?
X-rays carry
What type of materials do X-rays penetrate?
soft materials (like body tissue).
Why do bones absorb X-rays ?
Bones are dense materials
We can use X-rays to build a shaded image of bones and body tissue
What are the safety precautions when dealing with X-rays ?
Due to the dangerous nature of X-rays, exposure to X-rays should always be kept to a minimum.
People working with X-ray equipment should always shield themselves to prevent exposure to X-rays.
These people will place materials (metals or lead) between themselves and the X-rays.
Hat are the risks with X-rays ?
They are highly ionising (can damage body cells), even in low doses.
What are the uses of X-rays ?
Low-energy X-rays are used for medical and industrial imaging.
High-energy X-rays are used to treat cancer.
X-rays are also used for security purposes to detect weapons in airports (and other places).
Dentists often take X-ray images of a patient’s teeth. The dentist operates the X-ray machine from behind a wall. Why does the dentist take this precaution when it is the patient who receives the dose of X-ray radiation?
The patient is only exposed to X-rays for a very short period of time. The dentist, however, may be exposed many times a day and so, over time, would be exposed to a very large amount of X-ray radiation. By operating the machine remotely, the dentist reduces their exposure to X-rays.
Where is Ultraviolet light positioned on the EM spectrum ?
between X-rays and visible light
In lamps how does UV light work ?
UV photons excite (gives energy to) atoms. The atoms then release visible light.
In sun tanning how does UV light work ?
In sun tanning, UV excites (gives energy to) skin cells. The skin cells then change colour.
What are the risks of UV light ?
Exposure to too much ultraviolet light can cause skin burns, skin cancer and cataract formations in the eye
What are the uses of UV light ?
medical and forensic photography, air purification, water disinfection and medical therapy.
Ultraviolet light can also be used to detect fake bank notes
What in high visibility cycling jackets allow us to see cyclists at night ?
The Pigments (materials)
What are the risks of infra-red radiation ?
It can cause serious skin burns if emitted from high-intensity sources.
How does infra-red radiation increase the temperature of food ?
The frequency is high enough to excite particles in food. This increases their temperature.
How do Infra-red cameras detect a range of frequencies?
Infra-red cameras can detect a range of frequencies. These frequencies can be shown in different colours to depict images.
What are the uses of infra red cameras ?
Infra-red radiation is used in TV controls.
Infra-red can also be used for security purposes, such as in intruder alarms by detecting body heat.
Where are microwaves on the EM spectrum ?
6th type of wave
What are the risks of microwaves ?
Because humans are largely made up of water, exposure to microwaves could have a harmful effect.
What are radio waves used for ?
radio and TV communications.
Why are radio waves used for radio and TV communications ?
Because radio waves have long wavelengths, they can be transmitted (sent) around the Earth’s surface and around buildings without interference.
What are the risks of radio waves ?
At high intensities, radio waves can cause internal heating of living tissue with potentially harmful effects.
How are Electromagnetic waves produced ?
by electrical circuits and by changes in atoms.
These changes in atoms (or nuclei) can produce radiations of lots of different frequencies
How are radio waves produced ?
Oscillations (repeating variations) in electrical circuits can produce radio waves
When radio waves are absorbed by alternating currents what can happen ?
they can create an alternating current with the same frequency as the radio wave itself.
This means that radio waves can lead to oscillations in an electrical circuit.
Where do gamma rays originate from ?
changes in the nucleus of an atom.
In order of increasing frequency, what are the colours on the visible light spectrum ?
Red, Orange, Yellow, Green, Blue, Indigo and Violet.
What is visible light used in ?
We use visible light to see the world around us
And in fibre optics
Why is visible light used in fibre optics ?
We use visible light in optical fibres because it can be totally internally reflected.
This means that we can transmit signals (information) along optical fibres without the signals (information) getting lost.
What’s a good way to remember the colours, in order of increasing frequency?
(Richard Of York Gave Battle In Vain).
What is visible light a form of ?
of electromagnetic radiation
What determines whether an object is opaque, translucent or transparent ?
If the light is absorbed, reflected or transmitted when it hits an object.
What happens when light hits an opaque object ?
Opaque objects either reflect or absorb all light that hits them.
No light passes through.
What happens when light hits translucent objects ?
Translucent objects transmit light but the rays are scattered.
We cannot see objects clearly through translucent objects.
What happens when light hits a transparent object ?
Transparent objects also transmit light without scattering the rays.
We can clearly see objects on the other side of transparent objects
What are the two ways light can be reflected from a surface ?
Specular reflection and Diffuse Reflection
When does specular reflection happen ?
when light is reflected by a smooth surface in a single direction.
When does diffuse reflection happen ?
when light is reflected by a rough surface.
This is because the light is scattered.
Why are colours different colours ?
Because they have different wavelengths and frequencies
