Refraction occurs when a wave crosses a boundary from one medium to another. A wave entering a medium at an angle will change direction.Diffraction refers to the "bending of waves around an edge" of an object. Diffraction depends on the size of the object relative to the wavelength of the wave.

Refraction:
Refraction is the bending of light as it passes from one medium to another. When light travels from a medium with one refractive index to a medium with a different refractive index, it changes its speed and direction. This change in direction is caused by the change in the speed of light.

Explanation of Refraction:
- Refractive Index: Each medium has a characteristic property called the refractive index, which determines how much the light is bent when it passes through that medium. The refractive index is a ratio of the speed of light in a vacuum to the speed of light in the medium.
- Snell's Law: The behavior of light during refraction is described by Snell's law. It states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the refractive indices of the two media.
- Angle of Incidence and Refraction: The angle of incidence is the angle between the incident ray and the normal line (perpendicular) to the interface between two media. The angle of refraction is the angle between the refracted ray and the normal line.
- Refracted Ray: When light passes from one medium to another, it changes its direction and travels along a new path called the refracted ray.

Applications of Refraction:
- Lenses: Refraction is utilized in lenses to bend light and form images. Convex lenses converge light rays, while concave lenses diverge them.
- Prism: Refraction in a prism causes the dispersion of white light into its constituent colors, creating a rainbow effect.
- Mirage: Refraction of light in the Earth's atmosphere can cause the phenomenon of mirages, where distant objects appear distorted or displaced.
- Optical Fibers: Refraction is employed in optical fibers, which transmit light signals over long distances through total internal reflection.

Diffraction:
Diffraction is the bending or spreading of waves as they encounter an obstacle or pass through a narrow opening. It occurs when waves encounter an obstruction that is comparable in size to their wavelength.

Explanation of Diffraction:
- Huygens' Principle: Diffraction is explained by Huygens' principle, which states that every point on a wavefront acts as a source of secondary wavelets that spread out in all directions.
- Wavefront Bending: When waves encounter an obstacle or a narrow opening, the secondary wavelets interfere with each other, causing the wavefront to bend around corners or spread out after passing through an opening.
- Diffraction Pattern: The resulting pattern is characterized by dark and bright regions, known as interference fringes, which can be observed on a screen placed behind the obstacle or opening.
- Diffraction Grating: A diffraction grating is a device with a large number of equally spaced slits or lines that diffract light and produce a pattern of multiple interference fringes.

Applications of Diffraction:
- Interference Patterns: Diffraction is used to study the wave nature of light and other types of waves. It helps in understanding interference patterns and measuring wavelengths.
- X-ray Diffraction: Diffraction of X-rays is employed to determine the arrangement of atoms in crystals, providing valuable information in the field of crystallography.
- Acoustic Diffraction: Diffraction of sound waves is crucial in designing concert halls and auditor