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AS Physics Unit 2
Waves and Quantum Behaviour
Superposition and Coherence

Waves are not physical objects therefore they do not bounce off each other when they
collide.

Instead, they combine temporarily and then continue to travel as before. This combination is
called superposition.

The interference caused by superposition can be…

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Standing Waves

Standing waves are formed when waves are confined, such as on a length of string, and a
whole number of waves is produced in the time it takes one wave to go to the end and
back.

The effect of the moving pulses is to create a series…

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Two Source Interference

If waves from two sources are coherent then an interference pattern can be formed.

With Young's slits this interference pattern is a series of alternating bright and dark fringes
on a screen.

Points where the path difference from the two slits is a whole number of wavelengths…

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When light is shone on a metal it may or not emit electrons. Experiment showed that:

For a given metal, no photoelectrons are emitted when exposed to radiation below
its own threshold frequency.
The kinetic energy of the electrons ranged from 0 to a maximum, this maximum
increased with the…

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Hot things emit continuous spectra of visible and infrared radiation. If this is shone through a
cool gas the electrons absorb photons of the right energy to move up a level and so when
the light is split dark lines appear matching the bright lines of the emission spectrum.

Each…

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If the speed of the electrons is increased the rings of the diffraction patter become smaller,
which is predicted by the smaller wavelength given by the de Broglie equation.

Electrons also behave like waves in other situations, such as in Young's slits.

It has since been proven that all particles,…

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If objects are projected horizontally you may have to work out how long they take to fall
with suvat and then how far they go in that time.

If objects are projected at an angle resolve the original vector into horizontal and vertical
vectors, use the vertical as the initial…

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Work=force x displacement. The work is only the energy transferred, other types of energy
may be present in the system.

If the force is at an angle to the direction of motion only the component in the direction of
travel contributes to the work done.

Power = work done /…

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