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