C. Imaging
C. Imaging
Core
C.1 – Introduction to imaging
Nature of science:
Deductive logic: The use of virtual images is essential for our analysis of lenses and mirrors.
Understandings:
Thin lenses
Converging and diverging lenses
Converging and diverging mirrors
Ray diagrams
Real and virtual images
Linear and angular magnification
Spherical and chromatic aberrations
Applications and skills:
Describing how a curved transparent interface modifies the shape of an incident wavefront
Identifying the principal axis, focal point and focal length of a simple converging or diverging lens on a scaled diagram
Solving problems involving not more than two lenses by constructing scaled ray diagrams
Solving problems involving not more than two curved mirrors by constructing scaled ray diagrams
Solving problems involving the thin lens equation, linear magnification and angular magnification
Explaining spherical and chromatic aberrations and describing ways to reduce their effects on images
C.2 – Imaging instrumentation
Nature of science:
Improved instrumentation: The optical telescope has been in use for over 500 years. It has enabled humankind to observe and hypothesize about the universe. More recently, radio telescopes have been developed to investigate the electromagnetic radiation beyond the visible region. Telescopes (both visual and radio) are now placed away from the Earth’s surface to avoid the image degradation caused by the atmosphere, while corrective optics are used to enhance images collected at the Earth’s surface. Many satellites have been launched with sensors capable of recording vast amounts of data in the infrared, ultraviolet, X-ray and other electromagnetic spectrum ranges.
Understandings:
Optical compound microscopes
Simple optical astronomical refracting telescopes
Simple optical astronomical reflecting telescopes
Single-dish radio telescopes
Radio interferometry telescopes
Satellite-borne telescopes
Applications and skills:
Constructing and interpreting ray diagrams of optical compound microscopes at normal adjustment
Solving problems involving the angular magnification and resolution of optical compound microscopes
Investigating the optical compound microscope experimentally
Constructing or completing ray diagrams of simple optical astronomical refracting telescopes at normal adjustment
Solving problems involving the angular magnification of simple optical astronomical telescopes
Investigating the performance of a simple optical astronomical refracting telescope experimentally
Describing the comparative performance of Earth-based telescopes and satellite-borne telescopes
C.3 – Fibre optics
Nature of science:
Applied science: Advances in communication links using fibre optics have led to a global network of optical fibres that has transformed global communications by voice, video and data.
Understandings:
Structure of optic fibres
Step-index fibres and graded-index fibres
Total internal reflection and critical angle
Waveguide and material dispersion in optic fibres
Attenuation and the decibel (dB) scale
Applications and skills:
Solving problems involving total internal reflection and critical angle in the context of fibre optics
Describing how waveguide and material dispersion can lead to attenuation and how this can be accounted for
Solving problems involving attenuation
Describing the advantages of fibre optics over twisted pair and coaxial cables
Additional higher level
C.4 – Medical imaging
Nature of science:
Risk analysis: The doctor’s role is to minimize patient risk in medical diagnosis and procedures based on an assessment of the overall benefit to the patient. Arguments involving probability are used in considering the attenuation of radiation transmitted through the body.
Understandings:
Detection and recording of X-ray images in medical contexts
Generation and detection of ultrasound in medical contexts
Medical imaging techniques (magnetic resonance imaging) involving nuclear magnetic resonance (NMR)
Applications and skills:
Explaining features of X-ray imaging, including attenuation coefficient, half-value thickness, linear/mass absorption coefficients and techniques for improvements of sharpness and contrast
Solving X-ray attenuation problems
Solving problems involving ultrasound acoustic impedance, speed of ultrasound through tissue and air and relative intensity levels
Explaining features of medical ultrasound techniques, including choice of frequency, use of gel and the difference between A and B scans
Explaining the use of gradient fields in NMR
Explaining the origin of the relaxation of proton spin and consequent emission of signal in NMR
Discussing the advantages and disadvantages of ultrasound and NMR scanning methods, including a simple assessment of risk in these medical procedures
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