Author: haroonkhan
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CAN WE DETECT INDIVIDUAL PHOTONS?
Let’s do a back-of-the-envelope calculation of just how many photons are produced by a typical 60-W lightbulb: although we know that the filament acts as a blackbody, and thus produces a wide range of wavelengths, let’s take 600 nm as an average for our quick estimate. The energy of a photon is E = hf = hc/λ, so the energy…
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THE PHOTOELECTRIC EFFECT
In 1905, Albert Einstein took Planck’s proposal one step further by stating that light itself is a beam of discrete packets, like bullets from a machine gun. Einstein needed this assumption to resolve another troublesome inconsistency in physics, this one concerning the photoelectric effect, by which electrons may be ejected from a metal surface illuminated by…
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THE SEED OF QUANTUM PHYSICS: PLANCK’S FORMULA
Returning to our story about the Ultraviolet Catastrophe, Einstein suggested solving it by using a mathematical “trick” that had been proposed 5 years earlier by Max Planck when he was trying to improve upon the Wien approximation. Planck produced a formula that matched the data very well by assuming that the harmonic oscillators could not…
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Introduction
Next time you turn on an electric oven, pay attention to the way in which the color of its glow changes as it heats up. The glow is at first weak and dull red before it turns bright orange. At higher temperatures, such as those in a blacksmith’s metalworking oven, the glow becomes much brighter…
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THE DOPPLER EFFECT
Lastly, if you built at least one of the units to act as both a transmitter and receiver, you essentially have the heart of a police radar gun, and you may want to experiment with the interesting wave property of light called the Doppler effect. Connect the Gunnplexer’s detector diode output (mixer output) to an…
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DOUBLE-SLIT INTERFERENCE WITH MICROWAVES
A double-slit experiment with 3-cm microwaves will give you the basic understanding of how double-slit experiments are conducted in sophisticated quantum research that we will discuss in chapters 7 & 8. Just as so many of the other specialized particle detectors, the Gunnplexer receiver does not produce an image, so the interference pattern needs to…
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REAL-WORLD BEHAVIORS
As you collect data, remember that Gunnplexers, stripboards, and other microwave components do not behave exactly as do their ideal, theoretical counterparts. For example, data from real Gunnplexers approximate, but do not exactly lie on, the ideal curve of Figure 13b. You should also have observed that stripboards are far from ideal polarizers, since they attenuate…
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OPTICS WITH 3-CM WAVELENGTH “LIGHT”
Let’s start by experimenting with a polarizer that is actually made out of wires, such as the one shown in Figure 10. However, we’ll need a source of electromagnetic waves with sufficiently large wavelength. Fortunately, it is easy to generate and detect microwaves with a wavelength of around 3 cm, making it possible to experiment with…
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POLARIZATION
Polarization is an important characteristic of light that Maxwell’s electromagnetic theory was finally able to explain. Notice in Figure 8 that the electric field is shown to oscillate in one plane, while the magnetic field oscillates on a perpendicular plane. The wave travels along the line formed by the intersection of those planes. The electromagnetic wave shown in…
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LIGHT AS AN ELECTROMAGNETIC WAVE
Later, in the 1860s, Scottish physicist James Clerk Maxwell identified light as an electromagnetic wave. Maxwell had derived a wave form of the electric and magnetic equations, revealing a wave-like nature of electric and magnetic fields that vary with time. Maxwell figured out that an electric field that varies along space generates a magnetic field…