College Board-Aligned Original Notes
AP Physics 2: Algebra-Based Unit 13 Topic 1: Refraction, reflection, and absorption
Light changes direction, speed, or energy distribution when it interacts with material boundaries.
Unit 13: Geometric Optics. College Board exam weighting listed for this unit: 12%-15% of exam score.
What to Know
- Reflection sends light back from a boundary with equal incident and reflected angles.
- Refraction bends light because its speed changes in a new medium.
- Absorption transfers light energy into the material.
- Always connect this topic back to the larger unit: Geometric Optics.
Detailed Notes
Refraction, reflection, and absorption belongs to Unit 13: Geometric Optics. Light changes direction, speed, or energy distribution when it interacts with material boundaries. Start by identifying the system, the field or interaction involved, and which conservation law or model applies.
Key relationships: Reflection sends light back from a boundary with equal incident and reflected angles. Refraction bends light because its speed changes in a new medium. Absorption transfers light energy into the material.
Model to use: Draw a ray diagram at a boundary with the normal line, incident ray, reflected ray, and refracted ray. A clear AP Physics 2 model should label directions, signs, units, and the physical meaning of each variable.
AP-style move: Use the normal line and relative index of refraction to decide whether a ray bends toward or away from the normal. For free-response work, show the governing principle first, then connect the mathematical result back to the physical situation.
Key Vocabulary
Reflection
Change in light direction when light bounces from a boundary.
Refraction
Change in light direction when light enters a medium with different wave speed.
Absorption
Transfer of light energy into matter.
Index of refraction
A measure of how much light slows in a medium.
Normal line
A line perpendicular to a surface at the point of incidence.
Quick Practice
How would you explain Refraction, reflection, and absorption in one or two AP-style sentences?
Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.
Related Topics in This Unit
- Images from lenses and mirrors
Official Alignment
Reference and Attribution
AP Physics 2 concept reference: AP Physics 2: Concise Summary Notes by IITian Academy. EduCompanion used this source as a topic checklist and conceptual reference, then rewrote the study notes in original wording.