9. Wave phenomena
9. Wave phenomena
9.1 – Simple harmonic motion
Nature of science:
Insights: The equation for simple harmonic motion (SHM) can be solved analytically and numerically. Physicists use such solutions to help them to visualize the behaviour of the oscillator. The use of the equations is very powerful as any oscillation can be described in terms of a combination of harmonic oscillators. Numerical modelling of oscillators is important in the design of electrical circuits.
Understandings:
The defining equation of SHM
Energy changes
Applications and skills:
Solving problems involving acceleration, velocity and displacement during simple harmonic motion, both graphically and algebraically
Describing the interchange of kinetic and potential energy during simple harmonic motion
Solving problems involving energy transfer during simple harmonic motion, both graphically and algebraically
9.2 – Single-slit diffraction
Nature of science:
Development of theories: When light passes through an aperture the summation of all parts of the wave leads to an intensity pattern that is far removed from the geometrical shadow that simple theory predicts.
Understandings:
The nature of single-slit diffraction
Applications and skills:
Describing the effect of slit width on the diffraction pattern
Determining the position of first interference minimum
Qualitatively describing single-slit diffraction patterns produced from white light and from a range of monochromatic light frequencies
9.3 – Interference
Nature of science:
Curiosity: Observed patterns of iridescence in animals, such as the shimmer of peacock feathers, led scientists to develop the theory of thin film interference. Serendipity: The first laboratory production of thin films was accidental.
Understandings:
Young’s double-slit experiment
Modulation of two-slit interference pattern by one-slit diffraction effect
Multiple slit and diffraction grating interference patterns
Thin film interference
Applications and skills:
Qualitatively describing two-slit interference patterns, including modulation by one-slit diffraction effect
Investigating Young’s double-slit experimentally
Sketching and interpreting intensity graphs of double-slit interference patterns
Solving problems involving the diffraction grating equation
Describing conditions necessary for constructive and destructive interference from thin films, including phase change at interface and effect of refractive index
Solving problems involving interference from thin films
9.4 – Resolution
Nature of science:
Improved technology: The Rayleigh criterion is the limit of resolution. Continuing advancement in technology such as large diameter dishes or lenses or the use of smaller wavelength lasers pushes the limits of what we can resolve.
Understandings:
The size of a diffracting aperture
The resolution of simple monochromatic two-source systems
Applications and skills:
Solving problems involving the Rayleigh criterion for light emitted by two sources diffracted at a single slit
Resolvance of diffraction gratings
9.5 – Doppler effect
Nature of science:
Technology: Although originally based on physical observations of the pitch of fast moving sources of sound, the Doppler effect has an important role in many different areas such as evidence for the expansion of the universe and generating images used in weather reports and in medicine.
Understandings:
The Doppler effect for sound waves and light waves
Applications and skills:
Sketching and interpreting the Doppler effect when there is relative motion between source and observer
Describing situations where the Doppler effect can be utilized
Solving problems involving the change in frequency or wavelength observed due to the Doppler effect to determine the velocity of the source/observer
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