P13 - Electromagnetic Waves Flashcards
What is ionisiation?
The process by which atoms become charged
What is a radiation dose?
Amount of ionising radiation that a person receives
What is wave speed?
The distance travelled per second by a wave crest or trough
What is white light?
Light that includes all colours of the spectrum
What is the structure of an electromagnetic wave?
Electromagnetic waves are transverse waves that transfer energy. The vibrations come in the form of electric and magnetic fields that make up the EM wave. They oscillate 90* to the direction in which the wave is travelling (The electric field also oscillates 90* to the magnetic field).
What is are the properties of an electromagnetic wave?
- They are transverse waves.
- They can travel through a vacuum (they do not require a medium to travel through).
- They travel at the speed of light
- EM waves with a high frequency have high energy, while low frequency waves have low energy
- They form a continuous spectrum
What is an electromagnetic wave?
Electrical and magnetic disturbances that transfer energy from one place to another
What is the order of the EM spectrum (from long wavelength to short) (low frequency to high)
Radio Waves Microwaves Infrared Visible Light Ultraviolet Light X-rays Gamma radiation
What is the speed of light in a vacuum?
3.0x10^8
What is the equation for the speed of a wave?
Wave speed = Frequency x wavelength
What are the properties of a short wavelength carrier wave?
- More information carried
- More energy carried
- Shorter range (greater absorption by the atmosphere)
- The less they spread out
What are the properties of a long wavelength carrier wave?
- Less information carried
- Less energy carried
- Greater range (less absorption by the atmosphere)
- The more they spread out
What are the 3 types of ionising EM radiation?
- UV Light (higher energy UV rays ONLY)
- X-rays
- Gamma radiation
How are gamma rays produced?
Gamma rays are produced when unstable nuclei in radioactive substances decay and release energy in the form of EM waves
Describe the penetrating power of Gamma rays and X-rays
Gamma rays and X-rays both are highly penetrating as they have short-wavelengths (therefore carry much more energy than longer wavelength EM waves). Gamma rays have shorter wavelengths than X-rays and are therefore more strongly penetrating
What are the dangers of X-rays and Gamma radiation, and how do you protect against them?
They are highly penetrative and are also forms of ionising radiation. This means they may cause mutations in cells which may lead to a cancerous tumour forming. To protect against them you should wear a thick plate of lead
Describe how ionising radiation works?
High-frequency radiation (UV, X-ray, Gamma) can knock electrons out of a substance as it passes through. This process is known as ionisation. If it happens to the atoms of living cells it can damage the cell, causing mutation of genes and cancerous growth. At higher doses it can kill the cell
What are 2 advantages of using an X-ray?
- They can accurately show if bones are broken or teeth contain cavities
- They can be used to destroy cancerous tumours
What are 2 disadvantage of using X-rays?
- They are a form of ionising radiation, in high doses they may cause cancer
- They cannot distinguish between soft tissue
Why can Ultrasound waves be used to image organs and unborn babies?
Ultrasound waves are used to image unborn babies and organs inside the human body. This is because ultrasound waves are partially reflected at body organs. This is because body organs have a different density to surrounding tissue. This means some of the ultrasound waves are reflected and detected by the transducer and used to form an image.
Describe one use of ultrasound for medical treatment (not medical imaging)
destruction of kidney stones
What do waves not transfer?
Matter
What is an alternating current?
a current that repeatedly reverses its direction
Why are X-rays used to detect internal cracks in metal objects
The more dense an object is, the more X-rays it absorbs from an X-ray beam passing through it. This different amounts of X-rays received on the opposite side of the metal object can be used to detect if there is a crack inside the metal object
What is a film badge and what does it do?
A device containing photographic film which registers the wearer’s exposure to radiation. This allows the users exposure to radiation to be monitored
How can gamma radiation be used in sterilisation?
Gamma rays are extremely high energy. Exposing food to gamma rays kills 99% of disease-carrying bacteria and pathogens. They can also be used to sterilise and kill any harmful bacteria on medical instruments
How can organs made from soft tissue be imaged using an X-ray?
The organ can be filled with a substance called a contrast medium that absorbs X-rays. This enables the interanl surfaces in the organ to be seen on the radiograph.
What does a radiation dose depend on?
- The type of radiation used
- How long the body is exposed to the radiation
- The energy per second absorbed by the body from the radiation