Unit 4 - Day 3: Diffraction and Interference of Water Waves

Course/Unit: SPH4U/Wave Nature of Light Date: To be decided

Lesson Big Idea(s):
  • Diffraction.
  • Interference.
  • Two point source interference.

Overall Expectations:
E3: Demonstrate an understanding of the properties of waves and light in relation to diffraction, refraction, interference, and polarization.
Specific Expectations:
E2.1 use appropriate terminology related to the wave nature of light, including, but not limited to: diffraction, dispersion, wave interference, nodal line, phase, oscillate, polarization, and electromagnetic radiation [C]
E2.2 conduct inquiries involving the diffraction and interference of waves, using ripple tanks or computer simulations [PR].
E2.4 analyse diffraction and interference of water waves and light waves (e.g., with reference to two-point source interference in a ripple tank, thin-film interference, multiple-slit interference), and solve related problems [PR, AI]
Learning Goals:
By the end of the class you will understand:
  • The Diffraction of water waves.
  • Interference of water waves and using two point sources.
/ Success Criteria:
I know I have achieved the learning goals when I can:
  • Explain Diffraction, interference.
  • Explain the mathematics of two point source.
  • Calculate nodal lines

Expected Prior Knowledge:
  • SPH3U: Waves and Sound
  • SPH4U: 9.1 : Properties of Waves and Reflection
  • SPH4U: 9.2: Refraction and total internal reflection.

Before: Minds On

Time: / Description / Materials
10
min / Minds On: Do Now:
  • Page 458 #10. Write out answers and hand in. This will test if students did the homework or not, of course bright students will be able to do this if they didn't do the homework.
Take up Homework:
  • Check if there are any questions from previous homework.
/
  • Computer
  • Internet

03 min / Transition from Minds On to Action:
  • Use the simulation to start diffraction topic.

During: Action

Time: / Description / Materials
15
min / Action1: Observation Station:
  • Set up a ripple tank before class and have the students look at it. OR
  • Use the simulation

  • Use 9.3 worksheet.
/
  • Ripple tank
Or
  • Computer
  • Internet

22 min / Action 2:
  • Direct lecture on Diffraction.
-Conditions for strong diffraction to occur and explain the wavelength/width of the opening i.e. λ/w ratio.
  • Direct lecture on Interference :
-Constructive and destructive interference
-Coherent source.
-Conditions for interference.
-Node, Nodal lines, nodal lines.
-Derivation of two point source interference.
20 min / Action 3:
  • Homework problems ‐ p 468‐469 #1‐7 Complete as group activity. Split class into 7 groups. Each group to complete one question on chart paper and present answers to class.

After: Consolidation

Time / Description
5
min / Exit Ticket:
  • Use the “9.3 Interference Pattern exit ticket”.
Homework:
  • Questions1-7 page 469, Nelson Physics 12 (do the questions you did not do).