3.3.2.1
Interference |
The concept of path difference
and coherence.
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AT i Investigation of two-source interference with sound, light and microwave radiation. |
The laser as a source of
coherent monochromatic light used to demonstrate interference and diffraction |
Comparison with non-laser light;
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Students will not be required to describe how a laser works. |
Students are expected to show awareness of safety issues associated with using lasers. |
Young's double-slit experiment: the use of two coherent sources or the use of a single source with double slits to produce an interference pattern.
The appearance of the interference
fringes produced by a double slit system |
Requirements of two source and
single source double-slit systems for the production of fringes.
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where
w is the fringe spacing and
s is the slit separation |
Required practical 2: Investigation of interference effects to include the Young’s slit experiment and interference by a diffraction grating. |
Production of interference pattern using white light. |
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Students will be expected to describe and explain interference produced with sound and electromagnetic waves. |
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Appreciation of how knowledge and understanding of nature of electromagnetic radiation has changed over time |
| 3.3.2.2 Diffraction |
Appearance of the diffraction pattern from a single slit using monochromatic and white light. |
Qualitative treatment of the variation of the width of the central diffraction maximum with wavelength and slit width.
The graph of intensity against angular separation is not required. |
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The plane transmission diffraction
grating at normal incidence |
Use of the spectrometer will not be tested.
Optical details of the
spectrometer will not be required. |
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Derivation of the diffraction grating
equation |
Applications; e.g. spectral analysis of light from stars. |
Where n is the order number. |
| 3.3.2.3 Refraction at a plane surface
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Students should recall that the refractive index of air is approximately 1.
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Candidates are not expected to
recall methods for determining refractive indices. |
Refractive index of a substance
s:
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| Snell's Law of refraction at a boundary |
for a boundary between two different
substances of refractive indices n1 and n2 |
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| Total internal reflection |
including calculations of the critical
angle at a boundary between a substance of refractive index
n1 and a substance of lesser refractive
index n2 or air; |
Simple treatment of fibre optics including function
of the cladding with lower refractive index around central
core - limited to step index only;
Material and modal dispersion.
Application to
communications.
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Students are expected to understand the principles and consequences of pulse broadening and absorption. |
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