Grade 11 Physical Sciences · Waves, Sound and Light · Paper 1 (Physics)

Geometrical Optics Grade 11

Real Geometrical Optics past paper questions and answers, with each memo split into the ticks examiners give. Try one, mark yourself, and see exactly which skill cost you marks.

past paper questions: 5 past paper questions
skills: 3 skills
videos: 3 videos

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Question WE1 · Siyavula Grade 11 Physical Sciences, 5.5 Refraction, Worked example 1 · 2 marks

WE1 Calculate the speed of light through glycerine which has a refractive index of

1, 4729

.(2)

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Geometrical Optics skills

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4. Question WE4 · Siyavula Grade 11 Physical Sciences, 5.6 Snell's Law, Worked example 4 · 3 marks
WE4 A light ray passes from water to diamond with an angle of incidence of $75°$ . Calculate the angle of refraction (refractive index of water $1, 333$ , of diamond $2, 42$ ). Discuss the meaning of your answer.(3)
Show the memo (3 ticks)Memo
1. ✓
  Snell's law substitution $n_{1} sin θ_{1} = n_{2} sin θ_{2}$
  $1, 33 sin 75° = 2, 42 sin θ_{2}$
  $sin θ_{2} = 0, 531$
  1 mark · Apply Snell's law
2. ✓
  Angle of refraction $θ_{2} = 32, 1°$
  1 mark · Apply Snell's law
3. ✓
  MeaningThe light ray passes from a medium of low refractive index to one of high refractive index. Therefore, the light ray is bent towards the normal.
  1 mark · Explain refraction and total internal reflection
5. Question WE5 · Siyavula Grade 11 Physical Sciences, 5.7 Critical angles and total internal reflection, Worked example 5 · 2 marks
WE5 Given that the refractive indices of air and water are $1, 00$ and $1, 33$ respectively, find the critical angle.(2)
Show the memo (2 ticks)Memo
1. ✓
  Snell's law with 90° refractionAt the critical angle the angle of refraction is $90°$ :
  $n_{1} sin θ_{c} = n_{2} sin 90°$
  $θ_{c} = sin^{- 1} (\frac{n _{2}}{n _{1}}) = sin^{- 1} (\frac{1}{1 , 33})$
  1 mark · Apply Snell's law
2. ✓
  Answer $θ_{c} = 48, 8°$ for light travelling from water to air
  1 mark · Apply Snell's law

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