Physics- Electromagnetic Short Waves Flashcards
(7 cards)
What is Visible Light?
Visible light takes up the smallest range of wavelengths in the electromagnetic spectrum
White light is made up of a series of different colours, which may be dispersed using a prism or diffraction grating.
Each colour of the visible light spectrum has its own wavelength: red has the longest wavelength (next to infrared), and violet has the shortest wavelength (next to ultraviolet)
What is Ultraviolet light?
UV light triggers a chemical reaction in the skin which causes us to tan, however too much exposure (or exposure to certain wavelengths) could result in burns, or even skin cancer.
The ozone layer of the atmosphere filters out the most harmful wavelengths and various products are available to offer further protection.
The reaction triggered by the UV light is also useful in detecting security markings + initiating some chemical reactions.
What are X-rays?
X-Rays are produced by X-ray tubes in high voltage machines.
They can penetrate soft materials easily and are absorbed by denser materials, therefore they can be used to take images of the body, or in security screening at airports.
-As X-rays have roughly the same wavelength as the radius of an atom, they can be used for analysing crystal structures using diffraction.
-Both X-rays and gamma rays are forms of ionising radiation- they can change atoms/ molecules to ions, causing them to react in diff ways, resulting in damage to cells, mutations and cancer
What are Gamma rays?
-Gamma rays have the shortest wavelength and highest frequency of all waves in the electromagnetic spectrum. They are produced by the nuclei some unstable isotopes.
-In spit of the ionisation risks, gamma rays are highly penetrating, making them useful for applications such as sterilisation, detecting faults (both medical and non-medical) and radiotherapy.
How do we Use medical imaging?
-By using waves that are able to penetrate the body, we can diagnose problems + ensure that the correct treatment is given.
We can do this using X-rays, Gamma Rays and Ultrasound:
-The choice of waves depends on the purpose and the risks
-Ultrasound is safest (as it’s not ionising) but it’s not as penetrating
-Gamma Rays carry the greatest risk, but can give us the highest resolution images
How do we use X-Rays?
In a traditional X-Ray, a single image is taken from just one angle.
-The image is recorded on a photographic film, or as a digital image using a charged-coupled device
-There is a risk of medical staff receiving a little ionising radiation with each scan
-Therefore, precautions need to be taken (such as lead screens, or leaving the room)
How do we use CT scans?
CT scans (computerised tomography) expose the patient to more radiation, but can produce higher resolution three-dimensional images, leading to more accurate diagnosis.
-The bed gradually moves into the gantry, where the machine takes an image of a ‘slice’ of the body (a tomogram) - these images are put together to form the 3D image
