b

OCR

Specification A, Physics, 3883/7883

Electromagnetic waves
Candidates should be able to:
- describe the main features of the electromagnetic spectrum and recall that all
electromagnetic waves travel with the same speed in free space.
- recall the orders of magnitude of the wavelengths of the principal radiations from radio waves to gamma-rays.

Health physics - Option
Candidates should be able to:
- understand the nature of X-rays and give a simple description of their production.(d) describe the use of X-rays in imaging internal body structures including the use of image intensifiers and of contrast media.
- describe the use of a rotating beam in the CT (computerised axial topography) scanner.
- outline the principles of the production and of the detection of ultrasonic waves using
piezoelectric transducers.
- understand the principle of ultrasonic echosounding, including the importance of acoustic impedance, to obtain diagnostic information about internal structures.
- understand that acoustic impedance of a medium is dependent on its density and on the speed of the wave in the medium.
- understand why a coupling medium is required for effective ulstrasound techniques.
- outline the principles of magnetic resonance, with reference to precession of nuclei,
Larmor frequency, resonance and relaxation time.
- outline the use of MRI (magnetic resonance imaging) to obtain diagnostic information
about internal structures.
- discuss the preferred uses and relative advantages of X-rays, ultrasound and MRI in
examining internal structures.