Virtual+Labs+&+Activities

toc Photoelectric Effect
Part 1 10.French Physicist Louis de Broglie questioned, “If light exhibits dual wave-particle behavior, why can’t any particle of matter, such as an electron, exhibit a wave nature?” 11.The Heisenberg Uncertainty Principle reflects the wave-particle duality of light and matter: The more we know about matter as a particle (well-defined position), the less we know about its momentum (wavelength) and vice versa. 12.What did each of these scientists contribute to Quantum Physics? 13.How does a solar-powered calculator work? When light hits the solar plates, electrons are released to power the calculator. 14.How does your cell phone’s digital camera work? Photons hit millions of little solar panels which capture the light and intensity. The camera than digitally projects the image. 15.How does a laser work? The laser releases photons while only exciting a specific number of electrons. Electrons emit light in photons which create the laser beam. 16.How do solar panels work? When the solar panel is hit by light, electrons are released which give energy and the power.
 * 1) Upon what physical quantity does the color of any glowing body depend? The color of any glowing body depends on the temperature. If two given bodies are the same temperature, they will glow the same color. As the temperature increases of a body however, the color will become redder.
 * 2) As the cells in a flashlight get weaker, the filament appears redder. Why? When the cells in the flashlight get weaker they have less energy and therefore produce smaller frequencies. The filament appear red because it has the smallest frequency on the visible spectrum.
 * 3) The surface temperatures of Vega, our Sun, and Barnard’s star are 10,000 K, 6,000 K, and 3,000 K respectively. Which of these appears blue in color; red in color; yellow in color? Why? The hotter the body, the closer to the blue side of the visible spectrum the color of the body will be. Therefore, the body with the highest temperature, Vega, will be blue, the body with the lowest temperature, Bernard’s, will be red, and the body that’s temperature is in between will be yellow.
 * 4) What is the photoelectric effect? The experiment that provide when light shines on a metal surface, the surface emits electrons.
 * 5) As a mechanical analog of the photoelectric effect, consider a ball at rest in a depression. If a sufficient amount of energy, E, is given to the ball of mass, m, by the push of the hand, it will roll up the hill and escape with velocity v. Write an equation of energy conservation for this situation and explain each term in the equation by analogy to Einstein’s photoelectric effect equation. E = mv2 (
 * 6) An ultraviolet light discharges a negatively charged electroscope.
 * 7) The effect is known as __photoelectric effect__.
 * 8) Why isn’t the effect noticed when a glass plate is inserted between the zinc plate and the UV light? The UV light is required for the zinc plate to emit electrons. The glass plate however blocks the light from reaching the plate and does not allow for the process to occur.
 * 9) What does the work function usually denoted by **// Ψ //** represent? The work function represents the amount of energy needed for the plate to emit the electrons.
 * 10) Rewatch the video at about the 7 minute mark. The upper half of the screen shows an electron trying to escape from the surface of the metal. The bottom half is a graph. The vertical axis represents the electric potential energy of the electron. As you watch the video, notice that the electron slides along the bottom line and slips up the edge to the bottom of the work function line. This represents the most energetic electrons, the ones that will escape from the surface if photons strike the surface with energy equal to or greater than the work function. If an electron absorbs a photon of ultraviolet light with energy **//hf//** greater than **// Ψ //**, what will happen to the electron? Although the work function defines the amount of energy needed for the plate to emit electrons it is not an exact value. Therefore, if the electrons absorb energy greater than the work function it will detach from the plate.
 * 11) Use the table of work functions of various metals on page 1.
 * 12) If green light will cause the photoelectric effect to occur in sodium metal, for which other metals listed will it definitely also eject photoelectrons? Cesium, Potassium
 * 13) What would be the effect of doubling the intensity of the light used? Doubling the intensity of light has no effect.
 * 14) What would be the effect of changing the color of the light used, for example, from green to blue or ultraviolet? When the color of light is changed, the frequency changes as well and therefore requires a different work function because there is a different energy level.
 * 1) How did de Broglie relate a particle’s momentum to its wavelength? Combined Einstein and Planck’s theories to create his own equation p = h/wavelength.
 * 2) In the de Broglie model of the atom, if electrons are viewed as waves circling the nucleus, why do they have to exist in orbits that increase a whole wavelength at a time? It is only possible for waves to have constructive interference and reinforce each other at integer values.
 * 3) Waves produce an interference pattern. How can the pattern be explained in terms of particle of light? Once the light hits the screen, the different particles that make up the specific light scatter about the screen and form a specific pattern.
 * 4) To what do the white light spots correspond where the wave pattern hits the screen? Constructive interference
 * 1) How can a particle’s location be made more definite? By adding new momentums
 * 2) As the position of the wave becomes more definite, what happens to the momentum? Becomes less definite
 * 1) Planck – discovered light radiated in little bundles of energy
 * 2) Einstein – explained the photoelectric effect
 * 3) De Broglie – believed lights behaves similar to particles and waves
 * 4) Schrodinger – Said that if enough wave lengths were put together the result is a wave concentrated in a certain point like a particle
 * 5) Heisenberg – uncertainty principle

The answers to many of these (especially 12 - 16) seem very perfunctory. I hope that you know the material better than these responses would indicate.

Part 2

The "Show your Work" in all caps was supposed to clue you in... You must show work for all calculations, as always: equations used, numbers plugged in, etc.