Light And EM Spectrum Flashcards
What types of waves are EM waves?
Transverse
What does EM stand for?
Electromagnetic
What is an EM wave?
A transverse wave caused by oscillations in an electromagnetic field.
What are the vibrations and oscillations in an EM wave?
They are the changes in electrical and magnetic fields at right angles to the direction of wave travel
What are the 3 things that all electromagnetic waves do?
- transfer energy as radiation
from the source of the waves to an absorber - can travel through a vacuum
such as in space - travel at the same speed through a vacuum or the air
How fast does an EM wave travel through a vacuum?
Electromagnetic waves travel at 300,000,000 metres per second (m/s) through a vacuum.
What do EM waves form?
A continuous spectrum of waves
What is a spectrum?
A series of similar waves arranged in order of wavelength or frequenc
What does the continuous
spectrum of waves formed by EM waves include?
- waves with a very short
wavelength,high frequency and high energy - waves with a very long wavelength, low frequency and low energy
What is wavelength?
The length of a single wave, measured from one wave peak to the next.
What is frequency?
The number of waves produced each second. The unit of frequency is hertz (Hz).
What are the 7 EM waves in order from longest to shortest
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-ray
Gamma rays
What does an EM wave with a long wavelength also have?
Low frequency and low energy
What does an EM wave with a short wavelength also have?
High frequency
High energy
What does visible light contain?
the limited range of frequencies that can be detected by the human eye
What are the limited range of frequencies that can be seen by visible light, that can be detected by the human eye?
1.red light has the lowest frequencies of visible light
2.violet light has the highest frequencies of visible light
What does the behaviour of an EM wave in a substance depend on?
The frequency
What are radio waves used for?
communication such as broadcasting television and radio, communications and satellite transmissions.
Can radio waves be transmitted by air?
Radio waves are transmitted easily through air
Are radio waves damaging to us?
They do not cause damage if absorbed by the human body
Can radio waves be reflected?
they can be reflected to change their direction. These properties make them ideal for communications.
How can radio waves be produced?
Radio waves can be produced by
oscillations
in electrical circuits.
What happens when radio waves are absorbed by a conductor?
When radio waves are absorbed by a conductor
they create an
alternating current
What is a conductor?
A material which allows charge to move easily through it.
What is an alternating current?
Also called ac. An electric current that regularly changes its direction and size.
What happens once a radio wave is absorbed by a conductor and made an alternating current?
This electrical current has the same frequency as the radio waves. Information is coded into the wave before transmission, which can then be decoded when the wave is received.
How are TV and radio systems transmitted?
By an alternating current
What are microwaves used for?
Microwaves are used for cooking food, communications and for satellite communications
Are microwaves dangerous?
Intense sources of microwaves can be dangerous through internal heating of body cells.
can high frequency microwaves be absorbed by food?
High frequency microwaves have frequencies which are easily absorbed by molecules in food
What increases when food molecules absorb microwaves?
The
internal energy
of the molecules increases which causes heating
What is internal energy?
The total kinetic energy and potential energy of the particles in an object.
What can microwaves easily pass through? What does this mean?
Microwaves pass easily through the atmosphere, so they can pass between stations on Earth and satellites in orbit.
What is infrared light absorbed by?
Infrared light has frequencies which are absorbed by some chemical bonds
What happens to the internal bonds in a chemical when infrared light is absorbed?
The internal energy of the bonds increases when they absorb infrared light, which causes heating
How is infrared light useful?
This makes infrared light useful for electrical heaters and for cooking food
What do all object emit?
Infrared light
Can the human eye see infrared light? And if not what can?
The human eye cannot see this light, but infrared cameras can detect it.
What is thermal energy useful for?
This ‘thermal imaging’ is useful for detecting people in the dark.
What is visible light used in and why?
Television and illumination because we can see them
As well as television and illuminations what is visible light also used for?
is also used in fibre optic communications,
How does fibre optic communications work?
It’s where coded pulses of light travel through glass fibres from a source to a receiver.
Can we see ultraviolet?
No
Is UV dangerous?
It can have hazardous effects on the human body
What causes us to can or burn?
The ultraviolet light in the sun
What are fluorescent substances used in?
energy-efficient lamps
How is UV used in energy efficient lamps?
they absorb ultraviolet light produced inside the lamp, and re-emit the energy as visible light
How is UV used on bank notes?
Similar substances are used on bank notes to detect forgeries.
What does The hazardous properties of UV mean it will kill?
Bacteria-so it can be used for disinfecting water
What can cause electromagnetic waves to be generated or absorbed?
Changes in atoms and their nuclei
How are gamma rays produced?
Gamma rays are produced by changes in the nucleus of an atom
What are gamma rays a form of?
Nuclear radiation
What are High energy waves such as X-rays and gamma rays are transmitted through?
body tissues with very little absorption.
What does the very little absorption by the body tissues mean that gamma is useful for?
for internal imaging. X-rays are absorbed by dense structures like bones, which is why X-ray photos are used to help identify broken bones.
What are x rays used for?
used to help identify broken bones.
X-scanning the internal structure of objects
in airport security scanners.
What are gamma rays used for?
are used for sterilising food and medical instruments, and in the treatment and detection of cancer.
What 3 waves are types of ionising radiation?
Ultraviolet waves, X-rays and gamma rays
What is ionising radiation?
Radiation that is able to remove electrons from atoms or molecules to produce positively charged particles called ions.
What can ionising radiation do to the body?
Ionisation can have hazardous effects on the body
How can UV light harm the body?
Ultraviolet waves can cause damage to skin cells and eyes, and increase the risk of skin cancer
How can x-rays harm the body?
X-rays and gamma rays can cause the mutation of genes, which can lead to cancer
