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Waves and light

Describe wave properties and use wave speed, reflection, refraction and ray ideas.

12 free questions · Notes · Worked solutions

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What you will practise

  • Identify amplitude, wavelength, frequency and period.
  • Use wave speed=frequency×wavelength.
  • Describe reflection and refraction at boundaries.
  • Apply ray diagrams and simple image or shadow reasoning.

Revision notes

Wave properties

A transverse wave oscillates perpendicular to its direction of travel; a longitudinal wave oscillates parallel. Amplitude is maximum displacement, wavelength is one cycle length, frequency is cycles per second, and period=1/f.

Wave equation

Wave speed v=fλ. Use hertz for f and metres for λ to obtain m/s. The wave transfers energy without a net transfer of matter.

Reflection and refraction

Reflection follows angle of incidence=angle of reflection, measured from the normal. Refraction changes direction because wave speed changes at a boundary; frequency stays constant, while wavelength changes.

Light rays

Light travels in straight lines in a uniform medium. A ray diagram uses arrows to show direction. For a plane mirror, the image is virtual, upright, the same size, and the same perpendicular distance behind the mirror as the object is in front.

A worked example

A water wave has frequency 5 Hz and wavelength 0.8 m. Find its speed and period.

  1. Use v=fλ for wave speed.
  2. v=5×0.8=4 m/s.
  3. Period T=1/f=1/5=0.2 s.

4 m/s; 0.2 s

Try it yourself

These are original practice questions, not official past-paper questions. Practice points count correct final answers; working is not automatically assessed.

Choose a question to begin.
Question 1 · Standard1 practice point

A wave makes 20 complete cycles in 4 s. What is its frequency?

Need a hint?

Frequency is cycles per second.

Worked solution
  1. f=20÷4=5 Hz.
Question 2 · Standard1 practice point

A wave travels at 12 m/s and has frequency 3 Hz. Find its wavelength.

Need a hint?

Rearrange v=fλ.

Worked solution
  1. λ=v/f=12/3=4 m.
Question 3 · Standard1 practice point

A ray strikes a plane mirror at 35° to the normal. At what angle to the normal is it reflected?

Need a hint?

Apply the law of reflection.

Worked solution
  1. Angle of reflection equals angle of incidence.
  2. The reflected ray is 35° to the normal.
Question 4 · Standard1 practice point

Which statement about refraction is correct when light enters glass from air?

Need a hint?

The boundary changes wave speed, while frequency is set by the source.

Worked solution
  1. Refraction occurs because wave speed changes.
  2. Frequency remains constant across the boundary.
Question 5 · Foundation2 practice points

A wave has frequency 8 Hz and wavelength 0.5 m. Find its speed.

Need a hint?

Use v=fλ.

Worked solution
  1. v=8×0.5.
  2. v=4 m/s.
Question 6 · Standard2 practice points

A sound wave has frequency 250 Hz. Find its period.

Need a hint?

Use T=1/f.

Worked solution
  1. T=1/250 s.
  2. T=0.004 s.
Question 7 · Standard2 practice points

A wave travels at 18 m/s and has wavelength 3 m. Find its frequency.

Need a hint?

Rearrange v=fλ to f=v/λ.

Worked solution
  1. f=18/3.
  2. f=6 Hz.
Question 8 · Standard2 practice points

A ray makes an angle of incidence of 52° with the normal. Find the angle between the reflected ray and the mirror surface.

Need a hint?

First reflect at the same angle to the normal, then use complementary angles.

Worked solution
  1. Angle of reflection to normal=52°.
  2. The mirror surface is 90° to the normal, so angle to surface=90−52=38°.
Question 9 · Stretch3 practice points

A wave travels 90 m in 6 s and has frequency 5 Hz. Find its wavelength.

Need a hint?

First calculate speed, then use v=fλ.

Worked solution
  1. v=90/6=15 m/s.
  2. λ=v/f=15/5=3 m.
Question 10 · Foundation1 practice point

A plane mirror is 2.4 m from an object. How far behind the mirror is its image?

Need a hint?

A plane mirror image is the same perpendicular distance behind it.

Worked solution
  1. Object distance from mirror=2.4 m.
  2. Image distance behind mirror=2.4 m.
Question 11 · Foundation1 practice point

A transverse wave has 12 complete cycles in 3 s. Find its frequency.

Need a hint?

Divide number of cycles by elapsed time.

Worked solution
  1. f=12/3.
  2. f=4 Hz.
Question 12 · Standard2 practice points

A wave travels at 340 m/s and has frequency 170 Hz. Find its wavelength.

Need a hint?

Use λ=v/f.

Worked solution
  1. λ=340/170.
  2. λ=2 m.

Coverage and sources

Selected IGCSE concepts, with a mix of introductory and more demanding questions. Check your own specification. AI drafted; independent teacher review is pending. Editorial details.

Cambridge IGCSE Physics 0625 syllabus

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