Wave Phenomena: Diffraction

Diffraction is the bending, spreading, and overlapping of waves when they encounter an obstacle or pass through a narrow gap/slit.

Characteristics of Diffraction:

• Occurs with all types of waves: water waves, sound waves, light waves, radio waves, etc.
• Waves do not always travel in a straight line, diffraction allows them to bend around corners or obstacles.
• Diffraction can cause wave patterns to overlap, leading to interference patterns (especially visible in light experiments).

Dependence on Wavelength and Gap Size:

• The extent of diffraction depends on the ratio of wavelength to gap size.
• If gap ≈ wavelength: Strong diffraction, waves spread out widely.
• If gap ≫ wavelength: Weak diffraction, waves mostly pass straight with little spreading.
• If gap ≪ wavelength: Almost no diffraction; waves behave as if the gap is blocked.

Everyday Examples of Diffraction:

• Sound waves: You can hear someone talking around a corner because sound waves bend around walls (sound wavelengths are large, around 0.1–1 m, so diffraction is noticeable).
• Water waves: When water waves pass through a small gap in a barrier, they spread out into semicircular waves.
• Light waves: Light normally doesn’t bend much because its wavelength is very small (\(10^{-7}\) m). Diffraction of light is only noticeable with very tiny slits or diffraction gratings.
• Radio waves: Long-wavelength radio waves diffract around hills and buildings, allowing reception even without a direct line of sight.

Effects of Amplitude and Slit Width on Diffraction

Effects of Wavelength on Diffraction

Interference Patterns

Importance of Diffraction in Science & Technology:

• Used in diffraction gratings to split light into spectra.
• Helps explain why telescopes and microscopes have limits to resolution (diffraction limits sharpness).
• Enables communication technologies, since radio waves diffract over obstacles and allow signal transmission beyond line of sight.