Today’s agenda:

Review of Waves.You are expected to recall facts about waves from Physics 23.

Young’s Double Slit Experiment.You must understand how the double slit experiment produces an interference pattern.

Conditions for Interference in the Double Slit Experiment.You must be able to calculate the conditions for constructive and destructive interference in the double slit experiment.

Intensity in the Double Slit Experiment.You must be able to calculate intensities in the double slit experiment.

This experiment demonstrates the wave nature of light.

Consider a single light source, and two slits. Each slit acts as a secondary source of light.

Light waves from secondary slits interfere to produce alternating maxima and minima in the intensity.

Reference and “toys:” fsu magnet lab, colorado light cannon, wave interference, double slit.

Young’s Double Slit Experiment

Interesting reading: the double slit experiment and quantum mechanics.But don’t take it too literally.

How does this work?

Light waves from the two slits arriving at the detection screen in phase will interfere constructively

In phase—constructive.

Out of phase—destructive.

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Light waves from the two slits arriving at the detection screen in phase will interfere constructively and light waves arriving out of phase will interfere destructively. Another applet (useful).

How does this work?

Light waves from the two slits arriving at the detection screen in phase will interfere constructively and light waves arriving out of phase will interfere destructively.

Video, with some teasers about quantum mechanics.

Disclaimer! The video is part of an advertisement for a New Age religion, and ends up heading towards shaky ground.

See, for example, Schrödinger’s Cat:

“One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.”—Erwin Schrödinger

“The idea of a particle existing in a superposition of possible states, while a fact of quantum mechanics, is a concept that does not scale to large systems (like cats), which are not indeterminably probabilistic in nature.”—Wikipedia

Electron double slit applet.

You can find this video on Youtube. To avoid streaming it, I’ll play this in class.