# Phet photo electric effect lab 27

THE PHOTOELECTRIC EFFECT

Name ____________________________ Date __________________ Period _____

The photoelectric effect is one of the key experiments that supported early quantum theory. Light, prior to the early 20th century, was considered to be a wave phenomenon. In most ways, this idea reflects reality well—for instance, light is bendable when passed through a lens. The energy of a wave is given by amplitude of the wave squared, so a light wave of a certain frequency should be able to have any value for energy as long as there is a bright enough light source.

However, when red light was shone on a metal surface, no electrons were ejected even when the brightest red light sources were used. On the other hand, when blue light was shone on the same metal surface electrons were ejected even when the source of light was weak (and brighter blue lights ejected more electrons) How could this be? The energy didn’t seem to depend on the amount of light hitting the metal but instead the frequency of light that hit the metal.

Planck put us on the path leading out of this thicket of confusion when he theorized that light and other forms of energy comes in “packets” or discreet “bundles”. Light, in this theory, is considered to be a particle, which we now call a photon. The photoelectric effect was explained by Einstein when he conjectured that Planck’s bundles of energy (i.e. photons) were “knocking loose” the electrons—but only if the photons had enough energy to do the job (a two year old isn’t able to knock a football player off his feet, but a bull undoubtedly could). Einstein’s ideas gave further support to the theory that light energy really is not continuous with infinitely small increments of change (a wave), but is in fact “chunky”.

Today’s lab involves a simulation of the photoelectric effect. You will be checking various metals for the point at which they begin to shed electrons, based on a specific threshold frequency—the exact point when the photons have enough energy to knock the electrons loose. This energy is called the work function (W) for the metal. Different metals hold on to their electrons more strongly or weakly due to atomic structure, so the work function for various metals varies. The formula for calculating W is as follows:

hn = Ek + W

Where

• h is Planck’s constant
• n is the frequency of the light
• Ek is the kinetic energy of the ejected electron
• W is the work function

The kinetic energy of the electron refers to its actual movement once ejected. Ek can effectively be ignored if we just reach the amount of energy to loosen the electron but not get it moving (Ek in these circumstances will essentially have a value of zero). You will be trying to achieve the lowest possible speed for the electrons you eject from the virtual metal surface. W can be obtained by calculating frequency and using Planck’s constant. The work function will be in joules, so in order to compare to published lists of work function values—which are in electron volts—your final value will require conversion into this unit.

The “equipment” you will be working with looks like this:

1.         Bring up the internet and go to the following site:        http://phet.colorado.edu/index.php

2.         Look for “Run our Simulations”, click “On Line”, then “Light and Radiation” (in      the left hand column), then “Photoelectric Effect”, then “Run Now”.

3.         Keep battery voltage at 0. Turn light intensity up to 100%. You will be testing           sodium first (metals are changeable in the upper right hand box).

4.         Adjust wavelength to a value which just allows electrons to leave the surface at a      lowest possible speed.

5.         Calculate W in electron volts using the following values and formulas:

c = ln, where c = 2.998E17 nm/sec, l is in nm and n is in s-1

h = 6.626E-34 J×s

## 7.         Look up work function values on the internet. Identify the mystery metal, and          check the values obtained for the other metals.

Calculate the price
Pages (550 words)
\$0.00
*Price with a welcome 15% discount applied.
Pro tip: If you want to save more money and pay the lowest price, you need to set a more extended deadline.
We know how difficult it is to be a student these days. That's why our prices are one of the most affordable on the market, and there are no hidden fees.

Instead, we offer bonuses, discounts, and free services to make your experience outstanding.
How it works
Receive a 100% original paper that will pass Turnitin from a top essay writing service
step 1
Fill out the order form and provide paper details. You can even attach screenshots or add additional instructions later. If something is not clear or missing, the writer will contact you for clarification.
Pro service tips
How to get the most out of your experience with Australia Assessments
One writer throughout the entire course
If you like the writer, you can hire them again. Just copy & paste their ID on the order form ("Preferred Writer's ID" field). This way, your vocabulary will be uniform, and the writer will be aware of your needs.
The same paper from different writers
You can order essay or any other work from two different writers to choose the best one or give another version to a friend. This can be done through the add-on "Same paper from another writer."
Copy of sources used by the writer
Our college essay writers work with ScienceDirect and other databases. They can send you articles or materials used in PDF or through screenshots. Just tick the "Copy of sources" field on the order form.
Testimonials
See why 20k+ students have chosen us as their sole writing assistance provider
Check out the latest reviews and opinions submitted by real customers worldwide and make an informed decision.
Sociology
I am happy
Customer 454749, June 29th, 2020
English 101
Good job.
Customer 462899, April 26th, 2022
English 101
You guys rock! Plenty of work to spin it and personalize it. And most importantly, on time!
Customer 462833, April 9th, 2022
Education
great
Customer 463647, December 22nd, 2022
Military
Good job
Customer 456821, January 2nd, 2023
Education
Good work.
Customer 453707, March 27th, 2022
Excellent.
Customer 458115, May 16th, 2022
Statistics
Super professional and highly qualified. Excellent customer service.
Customer 462485, May 29th, 2022
Great
Customer 453413, February 27th, 2020
ASCI 491: Operational Applications in Aeronautics
Well articulated.
Customer 457731, April 12th, 2022
Perfect
Customer 463337, April 18th, 2023
Military
excellent
Customer 456821, September 1st, 2022
11,595
Customer reviews in total
96%
Current satisfaction rate
3 pages
Average paper length
37%
Customers referred by a friend
OUR GIFT TO YOU
15% OFF your first order
Use a coupon FIRST15 and enjoy expert help with any task at the most affordable price.
Claim my 15% OFF Order in Chat