Interactive Labs › Physics labs
PPhysicsS5 to S6Waves and light
Light lab: interference and diffraction
A laser pointer and an old CD are enough to measure the wavelength of light. See how light waves add up and cancel.
LevelS5 to S6 (and A Level)
TimeAbout 35 min
You usey = λD ÷ d, d sin θ = nλ
PriceFree: no account
🎯 Aim
To investigate interference and diffraction of light and to measure wavelength and grating spacing.
You will learn to
- Explain interference with path difference.
- Use y = λ D ÷ d.
- Use the grating equation d sin θ = n λ.
- Explain why this shows the wave nature of light.
🧭 What to do
- Choose the Red laser pointer and Two slits: read the fringe spacing.
- Change the slit separation and the screen distance.
- Change to green and violet light.
- Choose Diffraction grating (a CD) and read the angles of the orders.
- Answer the questions with the class data.
- Write your conclusion and download your lab report.
📋 The data
Measurements with a red laser, double slits and a CD.
🧠 Investigate: answer from the data
Type your answer and tap Check. Use 💡 Hint first; open the method only when you are stuck.
➕ Get more from this experiment
📝 Free
Print the worksheet (button above), download the data, and save your report. Teachers can project this page in class.
📦 Premium Lab Pack
1 000 RWF
- Practical worksheet: measure a laser wavelength with a CD (safety rules)
- Interference problems
- Teacher guide and answer key
- Exam-style questions with marking scheme
👩🏫 For teachers
Use it as a practical when apparatus is missing, as homework, or as a project. Free lesson plans help you plan, teach and assess.
🔗 Related in the subjects