Diffraction: Overview, Questions, Preparation

Diffraction is referred to the phenomenon which occurs when light rays bend or spread while passing through an edge or opening of the object. This bending of the light rays leads to the creation of some dark and light patterns or bands, known as interference fringes. These fringes are called constructive and destructive interferences.

This phenomenon is not visible to the naked eye if the size of the obstacle isn’t comparable with the light’s wavelength. Some common examples of diffraction include rainbow patterns on CDs, bending of light around corners of doors and windows, spreading of sound waves at corners, etc.

NCERT majorly recognizes the following types of diffraction which the candidates need to go through in order to clear their basic understanding of diffraction’s core concept:

Fresnel Diffraction

• In this type of diffraction, the source or the screen is placed at a finite distance from the object.
• The waves are spherical or cylindrical (curved) instead of plane.
• To observe the result, lenses may be required.
• Examples: diffraction around the edges of a sharp object.

Fraunhofer Diffraction:

• In this type of diffraction, the source or the screen is placed at an infinite distance from the object.
• The light waves in this case are plane waves.
• To observe the result, lenses are definitely required to make the light waves parallel.
• Examples: single slit diffraction.

Suppose a light of wavelength λ passes through an obstacle. The general formula for this equation will be:

asinθ=nλ

Where,

A = width of the slit

λ = light’s wavelength

n = 1,2,3…….

θ = angle of diffraction

There are numerous day-to-day implications of the concept of diffraction, as it is considered a very important concept in the field of physics. Some of the common ones are  specified below for candidate’s reference:

• Spectroscopy
• Holography
• X-Ray Crystallography
• Blue Colour of the Sky
• Microscopes and telescopes
• Radio Waves and Signals