Optics - Wave Optics - SS2 Physics Past Questions and Answers - page 3

Diffraction of light waves is the bending or spreading out of light waves as they encounter an obstacle or pass through an aperture. It occurs when a wave encounters an obstruction or a narrow opening that is of comparable size to its wavelength. Diffraction is a result of the wavefronts of the light waves interacting with the edges of the obstacle or aperture. The amount of diffraction observed depends on the size of the obstacle or aperture relative to the wavelength of light. When the size of the obstacle or aperture is smaller than the wavelength of light, the diffraction is more pronounced.

Diffraction is distinct from other wave phenomena such as refraction and reflection. Refraction refers to the bending of light waves as they pass from one medium to another, while reflection is the bouncing back of light waves off a surface. Diffraction, on the other hand, involves the bending or spreading out of light waves due to obstacles or apertures. It is a result of the interaction between the wavefronts and the edges of the obstacle or aperture, leading to a characteristic pattern of interference and diffraction fringes.

The extent of diffraction observed is influenced by two main factors: the size of the obstacle or aperture and the wavelength of light. When the size of the obstacle or aperture is smaller than the wavelength of light, the diffraction is more pronounced. This is because the edges of the obstacle or aperture cause significant interference and bending of the light waves. As the size of the obstacle or aperture approaches or exceeds the wavelength of light, the diffraction becomes less noticeable.

The wavelength of light also plays a crucial role in determining the extent of diffraction. Shorter wavelengths, such as those of blue or violet light, exhibit less diffraction compared to longer wavelengths, such as those of red or yellow light. This is because the shorter wavelength light waves are less affected by the edges of the obstacle or aperture, resulting in narrower diffraction patterns. Conversely, longer wavelength light waves are more prone to bending and spreading out when encountering obstacles or apertures, leading to broader diffraction patterns.

Diffraction of light waves finds numerous practical applications in various fields. One such application is in the design of optical devices such as diffraction gratings and holograms. Diffraction gratings consist of a series of closely spaced parallel slits or rulings that cause light waves to diffract and interfere, producing a pattern of bright and dark spots. They are used in spectroscopy to separate light into its constituent wavelengths and in optical instruments to disperse light for analysis.

Holography is another application of diffraction where interference patterns are recorded on a photographic medium. These recorded interference patterns produce three-dimensional images when illuminated by coherent light, creating realistic and detailed representations of objects. Holography has applications in security, data storage, and art.

Diffraction is also utilised in particle size analysis techniques such as laser diffraction. By passing a laser beam through a dispersed.