P3 | Flashcards

Question	Answer
Radiation in Medicane	Image: radiation (image/jpg)
using radiation to spot illnesses.	radiation can spot illnesses.
X-rays	electromagnetic radiation. take images of broken bones and some soft tissues.
CAT scans	Computer Axial Tomography. A 3D image of x-rays.
PET scanners	radioactive chemicals are either injected or swallowed. detectors called gamma cameras take images of the radiation emitted.
Endoscopes	Little cameras that go down your throat. commonly to the reproductive and digestive systems.
Ultrasound	has a frequency higher than human hearing. tissues and organs reflect these waves back. create images of unborn babies. also used to create images of tendons, muscles joints and some internal organs.
using radiation for treatment.	radiation can not only spot illnesses but treat them.
Radiation therapy	ionising radiation is used to treat diseases. used to control or kill cancer cells. It damages the DNA of the cells it is exposed to and therefore kills them.
Ultrasound	Ultrasound pulses can be used to break up kidney stones. The kidney stones can then pass through body. can also be used to treat internal injuries to help them heal faster.
Lasers	Lasers can be used in eye surgery to correct myopia and hyperopia. remodel the cornea. Lasers are also used to remove tattoos, hair and birth marks.
Radiation energy	Radiation is any form of energy originating from a source and includes both waves (eg light, sound or gamma rays) and particles (eg alpha and beta radiation).
Radiation	radiation spreads out from its source, it does so in all directions in a sphere of increasing size. The strength of the radiation decreases the further away from the source.
Radiation intensity	The intensity of emitted radiation can be calculated by using the following equation: intensity (W/m2) = power of incident radiation (W) ÷ area (m2) I = P ÷ A
I = P ÷ A	Calculate the intensity of a 200 W beam of radiation over an area 10 m2 I = 200 ÷ 10 Therefore the intensity = 20 W/m2
Reflection	Light rays reflect from surfaces. The angle at which a ray hits a surface (the angle of incidence) is always the same as the angle at which it is reflected (the angle of reflection).
specular reflection	smooth surfaces, such as mirrors, reflect all rays in parallel lines
diffuse reflection	rough surfaces scatter light rays in different directions
Refraction	When light passes at an angle from one transparent medium to another of a different density it changes direction.
refraction doesn't occur when light rays cross into a different medium at 90o.	Image: science_1 (image/png)
Image: science_2 (image/png)	Image: science_3 (image/png)
Total internal reflection	Waves going from a dense medium to a less dense medium speed up at the boundary. This causes light rays to change direction when they pass from glass to air at an angle other than 90º. This is refraction.
critical angle	ll the waves reflect back into the glass.
Image: 1 (image/png)	Image: 2 (image/png)
Image: 3 (image/png)	Image: 4 (image/png)
Image: 6 (image/png)	Image: 7 (image/png)
The critical angle for most glass is about 42°.	All light waves, which hit the surface beyond this critical angle, are effectively trapped.
Optical fibres	An optical fibre is a thin rod of high-quality glass. Very little light is absorbed by the glass.
Light getting in at one end undergoes repeated total internal reflection, even when the fibre is bent, and emerges at the other end.	Image: again (image/png)
optical fibres are used in endoscopes that allow surgeons to see inside their patients	optical fibres can also carry enormous amounts of information as pulses of light
Refraction of light by lenses	Light can be refracted by lenses. A lens is a piece of glass or plastic that has been shaped to refract light in a particular direction.
Converging lenses	These are thicker in the middle and focus light on a specific point called the focus. When the object being viewed is close to a converging lens, it acts like a magnifying glass. When the object is further away it appears smaller and upside down.
The distance from the focus to the middle of the lens is called the focal length.	Image: hhh (image/png)
Diverging lenses	These are thinner in the middle and are used to spread out light as it passes through the lens.
To determine the focus for a diverging lens, you trace the path of the light rays that have left the lens backwards to the point at which they converge. The distance from this point to the middle of the lens is the focal length. When an object is placed within the focal length of a diverging lens it is magnified and remains the correct way up.	Image: hik (image/png)
The lens equation	The lens equation allows us to calculate where an image will occur after passing through a lens.
1/focal length (m) = 1/object distance (m) + 1/image distance (m)	1/f = 1/u + 1/v
This can be rearranged to:	1/image distance = 1/focal length – 1/object distance
real image	if v is positive then the image is a real image.
virtual image	if v is negative then the image is a virtual image.

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