You can show for yourself that the threshold wavelength is nm blue light. This means that if calcium metal is used in a light meter, the meter will be insensitive to wavelengths longer than those of blue light.
Such a light meter would be completely insensitive to red light, for example. See how light knocks electrons off a metal target, and recreate the experiment that spawned the field of quantum mechanics. Skip to main content. Introduction to Quantum Physics. Search for:. The Photoelectric Effect Learning Objectives By the end of this section, you will be able to: Describe a typical photoelectric-effect experiment. Determine the maximum kinetic energy of photoelectrons ejected by photons of one energy or wavelength, when given the maximum kinetic energy of photoelectrons for a different photon energy or wavelength.
Example 1. What is the energy in joules and electron volts of a photon of nm violet light? Discussion The energy of this nm photon of violet light is a tiny fraction of a joule, and so it is no wonder that a single photon would be difficult for us to sense directly—humans are more attuned to energies on the order of joules.
PhET Explorations: Photoelectric Effect See how light knocks electrons off a metal target, and recreate the experiment that spawned the field of quantum mechanics.
Click to download the simulation. Run using Java. Conceptual Questions Is visible light the only type of EM radiation that can cause the photoelectric effect? Which aspects of the photoelectric effect cannot be explained without photons? Which can be explained without photons? Are the latter inconsistent with the existence of photons?
Is the photoelectric effect a direct consequence of the wave character of EM radiation or of the particle character of EM radiation? Explain briefly. Insulators nonmetals have a higher BE than metals, and it is more difficult for photons to eject electrons from insulators. Discuss how this relates to the free charges in metals that make them good conductors. If you pick up and shake a piece of metal that has electrons in it free to move as a current, no electrons fall out.
Yet if you heat the metal, electrons can be boiled off. Explain both of these facts as they relate to the amount and distribution of energy involved with shaking the object as compared with heating it. Is this in the visible range? Find the longest-wavelength photon that can eject an electron from potassium, given that the binding energy is 2. Is this visible EM radiation?
What is the binding energy in eV of electrons in magnesium, if the longest-wavelength photon that can eject electrons is nm? Calculate the binding energy in eV of electrons in aluminum, if the longest-wavelength photon that can eject them is nm.
What is the maximum kinetic energy in eV of electrons ejected from sodium metal by nm EM radiation, given that the binding energy is 2. UV radiation having a wavelength of nm falls on gold metal, to which electrons are bound by 4. What is the maximum kinetic energy of the ejected photoelectrons? Violet light of wavelength nm ejects electrons with a maximum kinetic energy of 0. Need even more definitions?
Just between us: it's complicated. Ask the Editors 'Everyday' vs. What Is 'Semantic Bleaching'? How 'literally' can mean "figuratively". Literally How to use a word that literally drives some pe Is Singular 'They' a Better Choice?
The awkward case of 'his or her'. Take the quiz. Our Favorite New Words How many do you know? Spell It Can you spell these 10 commonly misspelled words? He shrank, as from some one who inflicted pain as a child, unwittingly, to see what the effect would be. And so this is why the clever performer cannot reproduce the effect of a speech of Demosthenes or Daniel Webster. The well-known "cock and bull" stories of small children are inspired by this love of strong effect.
She stabbed him, noting the effect upon him with a detached interest that seemed indifferent to his pain. The emission of electrons from a metal when light shines on it. The effect is widely used to convert a light signal into an electric current see also current. New Word List Word List. Save This Word!
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