Reflection, Refraction, and Diffraction of Waves - SS2 Physics Lesson Note

Reflection, refraction, and diffraction are fundamental phenomena that occur when waves encounter boundaries or pass through different media.

Reflection:

Reflection is the bouncing back of a wave when it encounters a boundary between two different media. The law of reflection states that the angle of incidence (the angle between the incident wave and the normal to the boundary) is equal to the angle of reflection (the angle between the reflected wave and the normal to the boundary). The incident wave, the normal to the boundary, and the reflected wave all lie in the same plane. Reflection occurs for various types of waves, including light waves, sound waves, and water waves. The angle of incidence and the angle of reflection determine the direction in which the reflected wave propagates.

Refraction:

Refraction is the bending of a wave as it passes from one medium to another with a different optical density. When a wave enters a new medium at an angle, its speed and direction change due to the change in the medium's refractive index. The amount of bending depends on the angle of incidence, the refractive indices of the two media, and the wavelength of the wave. According to Snell's law, 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: n1 sinθ1 = n2 sinθ2. Refraction is responsible for phenomena such as the apparent bending of a straw in a glass of water and the formation of rainbows.

Diffraction:

Diffraction is the bending or spreading out of waves when they encounter an obstacle or pass through a narrow opening. It occurs when the size of the obstacle or opening is comparable to the wavelength of the wave. Diffraction causes waves to bend around corners and spread out into the regions behind obstacles, creating patterns of interference and spreading of energy. The amount of diffraction depends on the wavelength of the wave and the size of the obstacle or opening. Diffraction is most noticeable with waves such as sound waves, water waves, and light waves.

Understanding the principles of reflection, refraction, and diffraction is crucial for various applications. These phenomena play significant roles in fields such as optics, acoustics, communication systems, and engineering. They enable the design and optimization of devices like mirrors, lenses, prisms, and antennas. The study of these wave behaviours has led to advancements in areas such as imaging technology, signal processing, and waveguide design.