JNTU B.Tech I Year ENGINEERING PHYSICS - I Previous Question Paper (May - 2018 - R16)

In division of wavefront, the incident wavefront is split into two or more parts by using apertures, slits, or mirrors, which then act as coherent secondary sources to produce interference. This method typically requires a point source or a narrow slit.

In division of amplitude, the amplitude of the incident light wave is split into two or more parts by partial reflection or refraction at the surfaces of thin films or plates. These parts travel different paths and are later recombined to produce interference; this method is commonly used with extended sources.

Fraunhofer diffraction occurs when both the source of light and the screen are effectively at an infinite distance from the aperture or obstacle, meaning the incident wavefronts are plane and the diffracted rays reaching the screen are parallel. Key properties include:

• The source and the screen are at an effectively infinite distance from the diffracting element, typically achieved in practice using convex lenses to render incident light parallel and to focus diffracted rays onto the observation plane.
• The diffraction pattern is characterized by a central maximum of high intensity, flanked by secondary maxima and minima of rapidly decreasing intensity.
• The pattern is sensitive to the geometry of the aperture; for a single slit, the intensity distribution is governed by the sinc-squared function, where the width of the central maximum is inversely proportional to the width of the slit.