Refraction of light — KCSE Physics

KCSE Physics · 114 practice questions · 8 syllabus objectives

30 easy54 medium30 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

State conditions for total internal reflection; describe applications including optical fibres, prism periscopes, and mirages

State Snell's law and apply n = sin i / sin r to calculate the refractive index, angle of incidence or angle of refraction

Define critical angle and total internal reflection; calculate the critical angle using sin c = 1/n

Describe applications of total internal reflection (optical fibres, periscopes, binoculars, sparkling of diamonds)

State the laws of refraction and Snell's law; calculate angles of refraction at plane interfaces

Define refractive index; relate it to real/apparent depth, speed of light, and critical angle

Explain dispersion of white light by a prism; identify colours and the property that distinguishes them

Refraction of light

Sample Questions

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1
easySHORT ANSWER4 marks

Describe two practical applications of total internal reflection in technology. (4 marks)

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Part (a) — 4 marks
Optical fibres are used in telecommunications for efficient signal transmission. (1 mk)
Prism periscopes enable viewing over obstacles by reflecting light. (1 mk)
Mirages occur due to the bending of light rays in hot air, creating an optical illusion. (1 mk)
Reflective prisms are used in binoculars to invert images for correct orientation. (1 mk)
2
easySHORT ANSWER2 marks

State the two conditions required for total internal reflection to occur. (2 marks)

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Part (a) — 2 marks
Light must travel from an optically denser medium to a less dense medium. (1 mk)
The angle of incidence must be greater than the critical angle. (1 mk)
3
easySHORT ANSWER4 marks

When white light passes through a prism, it separates into its constituent colours. (a) Identify the colour that appears in the middle of the spectrum. (1 mark) (b) Name the two colours that are adjacent to the middle colour in the spectrum. (2 marks) (c) Explain the property of light that causes the separation of colours in a prism. (1 mark)

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Part (a) — 1 mark
Green (1 mk)
Part (b) — 2 marks
Yellow (right) (1 mk)
Blue (left) (1 mk)
Part (c) — 1 mark
Different wavelengths of light are refracted by different amounts. (1 mk)
4

A beam of white light enters a prism and emerges as a spectrum of colours. (a) Identify the colour that is least deviated when the light exits the prism. (1 mark) (b) Name the colour that is most deviated in the spectrum produced by the prism. (1 mark) (c) List all the colours present in the spectrum in the order of their deviation from least to most. (2 marks)

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