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16.0Reflection and Refraction

Overview: Reflection and Refraction: Mirrors, Refraction of Light and Lenses — American System Physics Revision Notes & Topical Questions

5 min read 7 parts Lesson 2 of 5 Unit quiz

📚 American System Physics Hub / Topical Revision
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Lesson summary

Apply the law of reflection.Light bends toward the normal entering a denser medium.Critical anglesinθc = n2/n1.Optical fibres use total internal reflection.Rainbows result from dispersion and internal reflection in droplets.Nearsightedness is corrected with diverging lenses; fars…

  • Light enters glass (n = 1.5) from air at 30°. Refraction angle?
  • A convex lens f = 10 cm, object 30 cm. Image distance?
  • Plane mirror image
  • Concave mirror
  • Convex mirror
  • Mirror/lens equation

Section 1 of 7Overview: Reflection and Refraction: Mirrors, Refraction of Light and Lenses

1
16.1 Reflection and Refraction: Mirrors,… concept map: Critical angle, Light enters glass (n = 1.5), A convex lens f = 10 cm, obje, Law of reflection, Plane mirror image
Visual guide to the key ideas explained in this lesson.
2
Negative di means a virtual image.
3
Negative m means inverted.
4
Chromatic aberration occurs in lenses due to dispersion.
5
Microscopes and telescopes combine lenses.
6
Mirages are caused by refraction in air layers.

Section 2 of 7Process & sequence

1
Draw principal rays (parallel, focal, centre).
2
Locate the image where rays meet.
3
Apply 1/f = 1/do + 1/di.
4
Calculate magnification.
5
Classify the image: real/virtual, upright/inverted, size.

Image by a convex lenswrite these steps in this order; each step is a marking point.

  1. Ray parallel → through F
  2. Ray through centre
  3. Rays meet
  4. Image located
  5. Describe image

Section 3 of 7Compare

Mirrors and lenses
DeviceTypeImages formed
Plane mirror—Virtual, upright, same size
Concave mirrorConvergingReal inverted (object beyond f) or virtual upright (inside f)
Convex mirrorDivergingVirtual, upright, smaller
Convex lensConvergingReal inverted or virtual magnified
Concave lensDivergingVirtual, upright, smaller
Indices of refraction
Mediumn
Vacuum/air1.00
Water1.33
Glass1.52
Diamond2.42

Section 4 of 7Worked examples

Light enters glass (n
1.5) from air at 30°. Refraction angle?
  • sinθ = 0.5/1.5 = 0.333, θ = 19.5°.
A convex lens f
10 cm, object 30 cm. Image distance?
  • 1/di = 1/10 − 1/30, di = 15 cm (real, inverted, smaller).

Section 5 of 7Key terms

Section 6 of 7Command terms

Command terms
Identify / Describe (FRQ)
A short, specific statement; describing requires relevant characteristics, not a single word.
Explain / Justify (FRQ)
Give the cause-and-effect reasoning or evidence; a restated fact does not score.
Calculate
Show setup, substitution and the answer with units.
Predict
State the expected outcome; add a reason only if asked to justify.
MCQ technique
Read every option; eliminate distractors that are true statements but do not answer the question; watch for NOT/EXCEPT.

Section 7 of 7Exam technique

Keywords the mark scheme looks for in this lesson

Keywords the mark scheme looks for in this lesson
Law of reflection · Plane mirror image · Concave mirror · Convex mirror · Mirror/lens equation · Magnification · Index of refraction · Snell's law · Total internal reflection · Dispersion
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.

How to get full marks (examiner guidance)

1
Answer exactly what is asked; extra correct material does not earn credit, and contradictory statements can cancel credit (AP FRQ).
2
Use precise vocabulary (e.g. “active site”, “concentration gradient”, “allele”), never “it/stuff/things”.
3
Show units and working in calculations.
4
In MCQs, predict the answer before reading the options, then eliminate.

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