We see beautiful nature through light, which is an electromagnetic wave. We hear sweet melodies through sound waves. Waves have numerous applications in everyday life, from cellular communication to laser surgery. If we drop a stone on a steady surface of the water, we will see a reflection on the surface of the water where the stone hits it. In today's modern technological world, the influence of mobile phones in our daily life is very high. It is an efficient means of sending messages from one point to another quickly and efficiently.
Electromagnetic waves are waves that differ from mechanical waves in that they travel at speeds equal to the speed of light in a vacuum. These waves are generated by accelerated electric particles. These waves are not mechanical because they can propagate without the help of any medium. The speed of these waves is equal to the speed of light in a vacuum. Electric field and magnetic field does not deviate from electromagnetic waves. Electromagnetic waves can cause interference effects and diffraction. And these are subject to polarisation. These are the properties of electromagnetic waves.
The set of EM waves arranged sequentially based on wavelength or frequency is called the electromagnetic spectrum. Radio waves, UV rays, microwaves, X-rays, infrared rays, and gamma rays are the types of electromagnetic waves.
Oscillators in an electrical circuit generate radio waves. Its wavelength is from 0.1m to 1000m. Such waves undergo reflection and diffraction.
Electromagnetic waves in an electrical circuit generate microwaves. Its wavelength ranges from 0.001m to 0.3m and its frequency ranges from $\mathrm{3\times 10^{11}Hz\:to\:1\times 10^{9}Hz}$. Such waves are subject to reflection and polarisation.
Heat sources ( also known as heat waves) produce infrared radiation. And infrared radiation is produced when molecules undergo rotational motion or vibration. Its wavelength is from $\mathrm{8\times 10^{-7}m\:to\:5\times 10^{-3}m}$ and the frequency range is $\mathrm{4\times 10^{14}Hz\:to\:6\times 10^{10}Hz}$.
Visible light is obtained from materials in the vapour phase. And excited atoms in gases also emit visible light. Its wavelength ranges from $\mathrm{4\times 10^{-7}m\:to\:7\times 10^{-7}m}$. The frequency ranges from $\mathrm{7\times 10^{14}Hz\:to\:4\times 10^{14}Hz}$. It is subject to refraction, diffraction, and polarisation.
Electromagnetic waves are transverse. Because the three vectors namely the oscillating electric field vector, propagation vector (the vector giving the direction of wave propagation) and the oscillating magnetic field vector are vertical to each other. An electromagnetic wave propagates in the X direction if both the electric field and magnetic field are in the Y and Z directions respectively. Electromagnetic waves do not reflect by electric fields and magnetic fields.
Maxwell’s prediction was empirically proven in 1888 by the scientific genius Heinrich Rudolf Hertz. The experiment setup is shown in the figure. This device consists of small metal spheres arranged as shown in the figure. These are connected to larger spheres. The other ends of the electrodes are connected to an induction coil of several turns. This system produces an electromotive force (emf). As the coil has a very high voltage, the air between the conductors becomes ionized and sparks (discharge sparks) and the small gaps between the conductors ( the conductors are not completely closed and are seen with small gaps in the ring). Energy is transmitted in the form of a wave from the terminal to the terminal (ring terminal). This wave is an electromagnetic wave. If the acceptor is rotated perpendicularly then the acceptor does not receive any spark. This confirms that electromagnetic waves are transverse according to Maxwell’s prediction.
Experimental circuit used by Heinrich Hertz in 1887
DMGualtieri, Hertz Transmitter Receiver, CC BY-SA 3.0
Radio waves are used in signal transmission and communication systems. Radio waves are also used for voice communication in mobile phones operating in ultra-high frequency bands.
Microwaves are used in radar equipment to guide aircraft and determine their speeds. Used in microwave cooking. It is also used for long-distance wireless communication via satellite.
Infrared rays provide power to the satellites in the form of solar cells. They use infrared rays to remove water from fruits and produce dry fruits. These are used as heat insulators in the greenhouse.
Infrared rays are used in thermotherapy to treat muscle pain and sprains. It is used in the remote control sensor used in the television set. Infrared rays are used for seeing oncoming vehicles in dim fog, night vision, and infrared photography.
Visible light spectrum used in photography. Visible light is used to examine the molecular structure, determine the arrangement of electrons in the outer shell of atoms and provide the eye with a sense of light.
UV rays can be used to kill bacteria, remove pathogens from surgical instruments, detect fingerprints in burglar alarms, detect hidden letters and learn molecular structure.
X-rays are more penetrating than UV-rays and X-rays are used more to study the structure of the shell inside the atom and to study the crystal structure.
X-rays are also used to diagnose bone fractures, detect bone and kidney stone formation and detect the growth of repaired bone.
Gamma rays are used to determine the structure of the nucleus. Gamma radiation is used to treat cancer. Gamma radiation is widely used in clinical practice.
Electromagnetic waves are generated by accelerated electric particles. These waves are not mechanical because they can propagate without the help of any medium. The set of electromagnetic waves arranged sequentially based on wavelength or frequency is called the electromagnetic spectrum. Radio waves, UV rays, microwaves, X-rays, infrared rays, and gamma rays are the types of electromagnetic waves. Microwaves are used in radar equipment to guide aircraft and determine their speeds. Infrared rays provide power to the satellites in the form of solar cells.
Q1. Characteristics of magnetic lines
Ans. Magnetic lines are continuous curves that penetrate the interior of the magnet. Magnetic field lines start at the north pole of the magnet and end at the south pole. These lines never cross each other. These are higher at the poles than at the center of the magnet.
Q2. Explain the line emission spectrum with an example
Ans. When a high-temperature gas passed through a prism, a line emission spectrum is obtained. A line spectrum can also be called a continuous spectrum. Each line represents the unique properties of the elements, that is different lines are available for different elements.
Q3. How is the continuous absorption spectrum obtained?
Ans. By passing light through a medium and then passing that light through a prism, the light archives diffraction. From this, continuous absorption can be obtained. For example, if you shine white light through blue glass, the glass will absorb all colors except blue.
Q4. Explain the spectrum obtained when white light is passed through diluted blood or plant greens?
Ans. A spectrum obtained after passing white light through iodine gas particles shows dark bands on a bright continuous white background. These black bands are band absorption spectra. Similarly, band absorption spectra can be obtained when white light is passed through dilute blood or plant sap or some mineral or organic solution.
Q5. How electromagnetic fields are used in the medical field?
Ans. Currently, electromagnetic fields play an important role in advanced medical equipment such as hyperthermia treatments for cancer and magnetic resonance imaging. Other devices based on electromagnetic technology write and scan information about the human body. Scanners, x-ray equipment, and many other medical devices use electromagnetic principles for their operation.
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