Electromagnetic waves, Lecture notes of Earth science

Download Electromagnetic waves and more Lecture notes Earth science in PDF only on Docsity! WEEK 4 LC10/ LC 11 Dispersion, scattering, interference, and diffraction are all phenomena related to the behavior of waves, including electromagnetic waves like light or sound waves. While they may seem similar, they describe distinct processes: Dispersion: 1. Dispersion refers to the separation of different wavelengths of a wave as it passes through a medium. This separation occurs because the velocity of a wave depends on its wavelength in certain mediums. Common examples of dispersion include the splitting of white light into its component colors when passing through a prism, or the separation of colors in a rainbow caused by the dispersion of sunlight in raindrops. Scattering: 2. Scattering occurs when waves encounter obstacles or irregularities in a medium and are redirected in various directions. Scattering can occur with any type of wave, including light, sound, or electromagnetic waves. The scattering process can be responsible for various phenomena, such as the blue color of the sky (Rayleigh scattering of sunlight in the atmosphere), or the diffusion of sound waves in a room due to interactions with surfaces. Interference: 3. Interference is the phenomenon that occurs when two or more waves interact with each other. It can result in either reinforcement (constructive interference) or cancellation (destructive interference) of the waves. Interference patterns can be observed in various contexts, such as the alternating bright and dark bands in a double-slit experiment with light or the patterns formed by overlapping ripples in water. Diffraction: 4. Diffraction is the bending or spreading of waves around obstacles or through openings. It occurs when waves encounter an obstruction that is comparable in size to their wavelength. Diffraction can cause waves to bend around corners or spread out after passing through a narrow slit, leading to characteristic patterns of intensity distribution. For example, the diffraction of light through a narrow slit results in a pattern of alternating bright and dark fringes known as a diffraction pattern. In summary, while dispersion, scattering, interference, and diffraction are all wave-related phenomena, they involve different mechanisms and produce distinct observable effects. LC 12 Heinrich Hertz was a German physicist who is credited with demonstrating the existence of electromagnetic waves, a crucial milestone in the development of radio technology. Hertz’s experiments were conducted in the late 19th century, building upon the theoretical work of James Clerk Maxwell. To produce radio pulses, Hertz utilized a setup consisting of several key components: 1. Spark Gap Transmitter: Hertz used a spark gap transmitter to generate electromagnetic waves. This device typically consisted of two metal spheres or electrodes separated by a small gap filled with air or another gas. When a high voltage was applied across the electrodes, it ionized the air in the gap, creating a conducting path. As the voltage increased, it eventually exceeded the breakdown voltage of the air, causing a spark to jump across the gap. The rapid discharge of electrical energy during the spark created a burst of electromagnetic radiation, including radio waves. 2. Induction Coil: Hertz used an induction coil to step up the voltage from a low-voltage power source to the high voltage needed to produce the spark. An induction coil consists of two coils of wire wound around a common iron core. When a current is rapidly switched on and off in the primary coil (the coil with fewer windings), it induces a high-voltage pulse in the secondary coil (the coil with more windings). 3. Antenna: Hertz employed an antenna to radiate the electromagnetic waves produced by the spark gap transmitter into space. The antenna acted as a conductor for the electromagnetic waves, allowing them to propagate through the air. 4. Receiving Apparatus: Hertz also developed a receiver to detect and measure the radio pulses he produced. His receiver typically consisted of a simple loop antenna connected to a spark gap or other device capable of detecting the electromagnetic waves.