5 - Reflection, Diffraction, Refraction (Schley)
Page 1: Introduction to Wave Behavior
Key Concepts:
Diffraction
Reflection
Refraction
Page 2: Agenda
Topics Covered:
Diffraction, Reflection, Refraction Notes (25 min)
Brain Break (5-10 min)
Wave Behavior Lab Design Handout (40 min)
Phet Simulation (if time permits)
Homework: Review notes as needed
Page 3: Wave Behavior
Key Question: What is causing these waves to change direction?
Key Principles:
Equal angles of reflection
Angle of incidence vs angle of reflection (Figure 1)
Page 4: Diffraction
Definition:
The spreading or bending of a wave as it passes through an aperture or around an obstacle.
Page 5: Reflection
Definition:
Change in direction of a wavefront at the interface between two different media, returning the wave into the original medium.
Law of Reflection:
Angle of incidence (i) = Angle of reflection (r)
Angles measured from the normal line.
All rays lie in the same plane: the plane of incidence.
Page 6: Reflection Practice Problem
Scenario: Light is incident on a flat surface, making an angle of 10° with that surface.
(a) Determine the angle of incidence.
(b) Determine the angle of reflection.
(c) Sketch the path of the reflected beam on the diagram.
Page 7: Reflection Practice Problem KEY
Answers for Problem:
(a) Angle of incidence = 10°
(b) Angle of reflection = 10°
(c) Illustration of path of the reflected beam.
Page 8: Refraction
Definition:
The travel of light (or other waves) from one medium to another, changing the wave's speed and thereby altering the direction of the incident ray.
Key Point:
Typically, both reflection and refraction occur when light strikes a surface.
Page 9: Brain Break!
Activity: Time away from academic activities to recharge.
Page 10: Wave Behavior Lab Design Handout
Focus: Understanding Diffraction
Activity: Observe the phenomenon of waves spreading around obstacles, as in natural bays.
Hypothesis Question: What happens when the opening to a bay decreases in size? Formulate using 'If, then, because...'
Visual Aids: Diagrams showing the effect of aperture size on wave behavior.
Page 11: Wave Behavior - Refraction and Reflection
Note: Phet simulation if time permits for a practical understanding of concepts.
Page 12: Deeper Understanding: Snell’s Law
Note: Snell’s Law is beyond the 9th-grade curriculum but relevant in IB Physics.
Purpose: Additional learning for interested students.
Page 13: Snell's Law Overview
Definition: Relationship between angles of incidence (θ1) and refraction (θ2) when light transitions between different media.
Formula: n1 sin(θ1) = n2 sin(θ2)
Where n1 and n2 are the refractive indices of the two media.
Page 14: Snell’s Law Practice Problem
Scenario: Light travels from crown glass (n=1.52) into air (n=1.00) with an angle of refraction in air of 60°.
Question: What is the angle of incidence in glass?
Page 15: Snell’s Law Practice Problem Continued
Problem Statement: Given: Light travels from crown glass (n=1.52) into air (n=1.00), with angle of refraction 60°.
Equipment: Calculator or online sine calculator for computation.