Planck Constant

1
Planck Constant

• Albert Hong
• St. Marks School

2
Why LED?

• Syllabus
• HKALE
• HKDSE Atomic World
• Let student familiar with the connection of the
  circuit a taste of electronics
• Cheap
• 0.5/LED
• With 200 for setting up 10 set for assessment

3
Structure
4
Formation of Depletion Layer
5
Forward Bias

• Current starts to flow when the potential
  difference is large enough to overcome the
  barrier created by the electric field.
• When electrons cross the boundary and move into
  holes, they move from higher-energy states to
  lower-energy ones. ? Photons emit.

6
Experiment (1)
7
Experiment (2)

• By changing the voltage supply, different
  currents can be obtained
• y-intercept the graph equals to hc/?q
• By giving students ?, h can be obtained

8
Experiment (3)

• The experiment can continue by giving students
  LED of unknown wavelengths
• Using h found to find unknown ?
• Blue, green or even IR

9
Apparatus

• Breadboard
• LED

10
Worksheet
11
Students work
12
Students work
13
Assessment

• Graph plotting technique suitable scale
• Extract information from unfamiliar situation
  no such experiment in most of the AL textbooks.
• 10 groups can be easily setup TAS can be done
  in the same session

14
Extension

• Can integrate with the experiment of finding
  wavelength with diffraction grating
• Use the ? found to obtain h
• Investigation different ways to find ? emitted
  by LED? Diffraction grating, circuit, etc.

15
Points to note

• Red LEDs spectrum is narrower Better if you
  are using the LED in diffraction grating
  experiment
• Start measurement from Vin 8-10V

16
(No Transcript)
17
Acknowledgment

• Perimeter Institute

18
Other resources

• About dark matter
• Simple enough for students with basic knowledge
  of gravitation and circular motion
• Video with worksheets for students
• http//www.perimeterinstitute.ca/index.php?option
  com_contenttaskviewid691Itemid657

19
More

• EinsteinPlus
• ISSYP