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A Guide for the Physics Depth Study – The Photoelectric Effect
A Guide for the Physics Depth Study – The Photoelectric Effect
Introduction
The photoelectric effect or photoemission (given by Albert Einstein) is the production of electrons or other free carriers when light is shone onto a material. Electrons emitted in this manner can be called photoelectrons.
Electrons are dislodged only by the impingement of photons when those photons reach or exceed a threshold frequency (energy). Below that threshold, no electrons are emitted from the metal regardless of the light intensity or the length of time of exposure to the light. To make sense of the fact that light can eject electrons even if its intensity is low, Albert Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets (photons), each with energy hf. This shed light on Max Planck's previous discovery of the Planck relation (E = hf) linking energy (E) and frequency (f) as arising from quantization of energy. The factor h is known as the Planck constant.
In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as the result of light energy being carried in discrete quantized packets. This discovery led to the quantum revolution. In 1914, Robert Millikan's experiment confirmed Einstein's law on photoelectric effect. Einstein was awarded the Nobel Prize in 1921 for "his discovery of the law of the photoelectric effect", and Millikan was awarded the Nobel Prize in 1923 for "his work on the elementary charge of electricity and on the photoelectric effect"
This is an open-source physics simulation based on codes written at Singapore by Fu-Kwun Hwang, Loo Kang WEE, Tze Kwang Leong.
In your Depth Study, you will investigate:
(1) the contribution of three scientists to the modern understanding of the nature of light; and
(2) conduct a firsthand investigation on the photoelectric effect.
When you have completed your investigation, submit your Depth Study Report.
Use the following sub-headings (descriptions are adapted from Kim, 2019):
· Title: A Depth Study of the Photoelectric Effect
· Introduction
- A motivational inquiry question that will lead to the investigation
- Write a paragraph stating what the report is about and why it is important
- Write an overall aim of the Depth Study
· Hypothesis
- This is a testable statement about the relationship between two variables
- In a Depth Study, there may be a several dependent variables tested at the same time.
· Literature Review: The Contribution of _____________ (Scientist 1), _____________ (Scientist 2) and Albert Einstein to the Modern Understanding of the Nature of Light.
- One paragraph for each scientist with a linking sentence to the next paragraph
- Christiaan Huygens and his wave theory of light;
- Sir Isaac Newton and his corpuscular theory of light;
- Thomas Young and his evidence for the wave theory of light;
- Etienne-Louis Malus and his evidence for light being a transverse wave;
- Phillip Lenard and his evidence of the photoelectric effect;
- Wilhelm Wien and his thermodynamic theory of radiation from hot objects; or
- Max Planck with his quantum theory of cavity radiation.
- A linking paragraph showing how this literature review yields a testable hypothesis
· Method
- Simple numbered list of points, each beginning with a verb (present tense command)
- Method A: physical experiments testing the photoelectric effect with zinc plate under various light exposures
§ Fluorescent light
§ UV-A torch
§ Sunlight
§ High-voltage electrical spark
- Method B: simulation experiment testing the photoelectric effect with various metals and light wavelengths
§ Choose the independent variables as metal, wavelength and intensity of light
§ Use repetition loops
· Risk Assessment
- Make a table
- Identify the risks / hazards, rank the risks (HAZPAK Rank) and minimise the risks
· Results
- Qualitative observations from the physical experiments (past tense)
- Table of quantitative results for the simulation experiment for dependent variables current, stopping voltage, work function
· Quantitative Analysis of Results
- Any calculations and work function equation for each metal.
- Present tense, e.g. The average time taken in Table 1 shows that it is independent of horizontal velocity.”
· Qualitative Analysis of Results
- Evaluation of the validity of the method
- Evaluation of the reliability of the results
- Description of some errors in the physical experiments
· Discussion
- Summarise and explain the results of your experiment
- Discuss the significance of your results
· Conclusion
- Answer the aim and state what the experiment has contributed in understanding the problem (inquiry question) posed.
· References
- List your references in alphabetical order according to author’s surname
- Don’t use wikipedia.com or google.com in this list
Reference:
Kim, DJ, Learnable (2019), How to Plan and Conduct Physics Practical Investigations, internet, https://www.learnable.education/how-to-study-and-ace-hsc-physics-study-guide/physics-practical-investigations/
A Guide for the Physics Depth Study – Wave Nature of Light
A Guide for the Physics Depth Study – Wave Nature of Light
Description of the task:
You task is to:
1. Study the contribution of three scientists to the modern understanding of the nature of light; and
2. Conduct a firsthand investigation on the wave model of light using an analyser with two polarising filters and a light meter.
Suggestions for revision:
Students are advised to:
Read through your class notes relevant to the learning outcomes.
Make summary notes from your textbook Physics in Context 12 Chapter “The Wave Nature of Light”.
Read the article by National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved 11 May 2021 from NASA Science website: http://science.nasa.gov/ems/02_anatomy.
Read the article by Fabrizio Logiurato (n.d.) “Teaching Light Polarization by Putting Art and Physics Together” at https://arxiv.org/ftp/arxiv/papers/1803/1803.09645.pdf.
Watch “Malus' law” (3:54) https://www.youtube.com/watch?v=utY72MD-Ii4
Guide for construction of analyser:
Students are required to make an analyser that can be used to:
Allow white light to pass through a polarising filter and an analysing filter
Adjust the angle between the two filters
Measure the intensity of the light after passing through the two filters
Equipment:
2 foam cups
2 polarisiing filters
Protractor
Permanent marker
Lux Light Meter (app on mobile phone)
Photo:
Google Sites
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