Category: Light As Particles

Einstein made very convincing arguments for the particle nature of light. However, as we saw Young’s experiments with the interference of light, and Maxwell’s explanations about the polarization of electromagnetic waves had already destroyed Newton’s view of light as a stream of particles. So where does this leave us? Suffice it to say that the… Continue reading WHERE DOES THIS LEAVE US?

All of the experimental demonstrations above have looked at the particle nature of light using billions of photons. Wouldn’t it be more convincing if we could observe a single particle of light at a time? The setup of Figure 33 gives us an opportunity to detect individual photons. The detector is the PMT probe that we just… Continue reading LISTENING TO INDIVIDUAL PHOTONS

Ideally, you should power your PMT from a lab-grade, low-noise, high-voltage power supply designed specifically to bias detectors. However, achieving exceptionally low ripple and high stability in a high-voltage power supply is not trivial, making these power supplies pricey. Designs for these low-noise power supplies are secrets closely guarded by companies that specialize in such… Continue reading LOW-COST PMT POWER SUPPLIES

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… Continue reading CAN WE DETECT INDIVIDUAL PHOTONS?

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… Continue reading THE PHOTOELECTRIC EFFECT

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… Continue reading THE SEED OF QUANTUM PHYSICS: PLANCK’S FORMULA

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… Continue reading Introduction