Diffraction Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Diffraction.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The spreading of a wave as it passes through a gap or around the edge of an obstacle.

Waves 'bend around corners'—you can hear someone even if you can't see them.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Diffraction is significant when the opening is comparable to the wavelength.

Common stuck point: Larger wavelength = more diffraction. Radio bends around buildings; light doesn't.

Sense of Study hint: When analysing a diffraction problem, compare the wavelength of the wave to the size of the gap or obstacle. If they are similar, expect significant spreading. For single-slit diffraction, minima occur at angles satisfying a\sin\theta = m\lambda where m is a nonzero integer and a is the slit width.

Worked Examples

Example 1

easy
Sound waves (\lambda = 1 \text{ m}) pass through a doorway 0.8 \text{ m} wide. Do the sound waves diffract significantly? Explain why you can hear someone around a corner.

Solution

  1. 1
    Diffraction is most significant when the wavelength is comparable to or larger than the gap size.
  2. 2
    Here \lambda = 1 \text{ m} > 0.8 \text{ m} (gap width), so significant diffraction occurs.
  3. 3
    The sound waves spread out as they pass through the doorway, which is why you can hear people in other rooms even without a direct line of sight.

Answer

\text{Yes, significant diffraction occurs because } \lambda \geq \text{gap width}
Diffraction is the bending and spreading of waves around obstacles or through gaps. It is most noticeable when the opening or obstacle is similar in size to the wavelength of the wave.

Example 2

medium
Light of wavelength 600 \text{ nm} passes through a single slit of width 0.1 \text{ mm}. At what angle does the first minimum of the diffraction pattern occur?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Visible light (\lambda \approx 500 \text{ nm}) and radio waves (\lambda \approx 1 \text{ m}) both encounter a building 10 \text{ m} wide. Which wave diffracts more around the building? Why?

Example 2

hard
A diffraction grating has 500 \text{ lines/mm}. Light of wavelength 650 \text{ nm} passes through it. At what angle does the second-order maximum appear?
← Back to Diffraction Practice Mode

Background Knowledge

These ideas may be useful before you work through the harder examples.

waveswavelength