Unit 3: 1 - Medical Applications of Physics Flashcards
What are Charge-coupled devices?
CCDs can be used to form electronic
What properties do X-rays have?
A high frequency and a low wavelength.
What are CT scanners?
Devices that use X-rays to produce digital images of a cross-section through the body (some organs can be filled with a contrast medium that absorbs X-rays so they can be seen on an X-ray image).
How can X-rays be used for therapy?
They can treat cancerous tumours on or near the body’s surface.
What are ultrasound waves? What are their frequencies?
Sound waves of higher than the human audible range (>20kHz). With an ultrasound scanner, the frequencies are usually between 2.5 and 10 MHz.
What is the equation for distance travelled by an ultrasound pulse?
s = v x t Displacement = Velocity x Time
What wavelengths do electromagnetic waves have?
0.01-1nml
How much background radiation is a dental or limb X-ray worth?
A few days.
Why do medical professionals choose to use ultrasound for scans?
Because it is non-ionising, so it does not carry the cancer risk that X-rays do.
How can ultrasound waves be used in therapy?
To shatter kidney stones..
Define the term refractive index.
A measure of how much the substance can refract a light ray.
Give the equation for the refractive index of a substance.
n = sin(i)/sin(r)
Refractive index = sin(Angle of incidence)/sin(Angle of refraction).
What is the critical angle of an object?
Where a ray is shone into the object, the critical angle is the angle of incidence when the angle of refraction emerges along the boundary..
What is an endoscope?
A device containing bundles of optical fibres which can look inside a patient’s body without cutting it open.
What is total internal reflection?
When the angle of incidence is equal to the angle of reflection, and the light does not leave the medium.
