Slides in this set
Medical Imaging X-rays
CCDs (charged coupled devices) are silicon chips
made up of millions of pixels that detect X-rays/light
and produce electronic signals to form high
resolution image. Used in digital cameras.
CT stands for Computerised axial Tomography it's
used for planning complicated surgery.
For treating cancer X-rays are focused on the
tumour using a wide beam which is rotated round
the patient.…read more
Medical Imaging - Ultrasound
Ultrasound can be used in industry to find cracks
in metal or to clean jewellery.
Ultrasound is partially reflected, partially
We use Distance = Speed x Time to find out the
distance between boundaries, but the result
must be halved as the ultrasound has gone there
and back.…read more
The change of speed of a wave is what causes
refraction when it enters a new medium.
When a wave slows it bends towards the normal.
If a wave hits a boundary at 90º it will not change
When light hits a different medium some is reflected.
Refractive index of a medium is the ration of speed of
light in a vacuum to speed of light in that medium.…read more
Magnification & Power
Magnified objects produce a virtual image. The object
MUST BE CLOSER TO THE LENS THAN THE FOCAL
Magnification = image height ÷ object height
A powerful lens has a short focal length because Power (in
dioptres) = 1 ÷ focal length (m).
Converging lens: power positive +
Diverging lens: power negative
The focal length is determined by the refractive index of
the lens material and the curvature of the lens material.…read more
Cornea and lens do most of the focusing
Iris and pupil sort out light intensity
Retina has light-sensitive cells which detect light
and sends a signal to the brain
A camera and eye produce real, inverted,
diminished images. The CCD in the camera is
the equivalent of the retina.…read more