After this lesson, you should be able to:

• Define wavefront as an imaginary line connecting points of the medium that are in phase
• State Huygens’ principle
• Define diffraction as the ability of a wave to spread out after an obstacle or aperture
• Apply Huygens’ principle to explain diffraction qualitatively
• Explain the formation of bright and dark fringes of light in terms of constructive and destructive interference of secondary wavelets
• Sketch the light diffraction pattern formed by a single slit
• Understand that the degree of diffraction is proportional to the wavelength and inversely proportional to the slit width
• Appreciate that the diffraction of light demonstrates its wave nature