Topic 1- Radiation and Treatment Flashcards
both ionising and non- ionising radiation are used in
medicine
X-rays are used for
medical imaging
x-rays are high energy and get absorbed by
dense materials like bone and metal
X-rays have a
health risk
CAT scans use
X-rays
CAT scans produce an image of a
2D slice through the human body
CAT scans are different from usual X-rays because they can produce an image of
soft tissue too
Endoscopes use
optical fibres
visible light is
non-ionising
endoscopes are good because it prevents
invasive surgery
ultrasound has a frequency of
more than 20000 Hz
ultrasound in
non-ionising
ultrasound can be used for
breaking down kidney stones, pre-natal scanning, measuring the speed of blood flow
radiation is energy that
originates from a source
Power=
I x A
intensity of radiation depends on
distance from source
intensity of radiation also depends on
what i t is passing through
the more dense the medium,
the more radiation will be absorbed
refraction is a change in direction caused by
a change in speed
convex lenses
converge light rays
concave lenses
diverge light rays
remember how to do ray tracing diagrams
yes
if the object is at 2F
real image, inverted,same size as object at 2F
if the object is between F and 2 f
real image, inverted, bigger and further than 2F
if the object is closer than F
virtual image, right way up, on same side, and bigger
power of lens=
1/focal length
1/f=
1/u + 1/v
for the eye you need to know the
basic structure
the iris is
the coloured part of the eye
the pupil is
the hole in the middle of the iris
the cornea is
transparent
the light is focused on the
retina
the lens is controlled by
the ciliary muscles
the far point is
the furthest distance that the eye can focus comfortably
the near point is
the closest distance the eye can focus on
on average, distances are
infinity, and 25 cm
short sighted people can’t focus on
distant objects
long sighted people can’t focus on
close objects
short sight can be corrected with
diverging lenses
long sight can be corrected with
converging lenses
sight can be corrected with
contact lenses or laser eye surgery
treatment for vision defect depends on
patient
every transparent material has
a refractive index
snell’s law says
n= sin i/ sin r
total internal relfection depends on
angle of incidence
greater than critical angle means that
no light comes out and all is totally internally reflected
critical angles can be found using
snell’s law
sin C=
refractive index of where the light is travelling to/ refractive index of where the light starts from
