Concept Of Waves And Electromagnetic Waves
Concepts to remember for JEE and CBSE board exams on the of Waves and Electromagnetic Waves
Wave motion:
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Characteristics of waves:
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Wavelength: the distance between two consecutive troughs or crests of a wave.
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Frequency: the number of waves passing a fixed point in one second.
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Amplitude: the maximum displacement of a particle from the equilibrium position.
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Wave velocity: the speed at which a wave travels through a medium.
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Transverse and longitudinal waves:
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Transverse waves: the particles of the medium vibrate perpendicular to the direction of propagation of the wave.
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Longitudinal waves: the particles of the medium vibrate parallel to the direction of propagation of the wave.
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Simple harmonic motion: a periodic motion where the restoring force is directly proportional to the negative displacement from the equilibrium position.
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Equation of a progressive wave: (y(x, t) = A \sin (kx-\omega t)), where (A) is the amplitude, (k) is the wave number, (x) is the position, (t) is the time, and (ω) is the angular frequency.
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Superposition of waves: When two or more waves meet at a point, the resultant displacement is the sum of the individual displacements of each wave.
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Standing waves: Formed when two progressive waves of the same frequency and amplitude travel in opposite directions and interfere with each other.
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The process by which energy is built up in a vibrating system is called resonance.
Electromagnetic waves:
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Properties of electromagnetic waves:
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Speed of light: (c = 3.00 \times 10^8) m/s.
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Frequency range: from (10^0 ) Hz to (10^{26}) Hz.
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Wavelength range: from (10^8 ) m to (10^{-12}) m.
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Electromagnetic spectrum: -Radio waves (wavelengths from 100 m to 10 km) -Microwaves (wavelengths from 1 mm to 30 cm) -Infrared radiation (wavelengths from 700 nm to 1 mm) -Visible light (wavelengths from 400 nm to 700 nm) -Ultraviolet radiation (wavelengths from 10 nm to 400 nm) -X-rays (wavelengths from 0.01 nm to 10 nm) -Gamma rays (wavelengths less than 0.01 nm)
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Generation and detection of electromagnetic waves:
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Electromagnetic waves are generated by charged particles undergoing acceleration.
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Electromagnetic waves are detected by devices that respond to their oscillating electric and magnetic fields.
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Polarization of electromagnetic waves:
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For a transverse wave, the direction of oscillation of the electric field vector is called the polarization of the wave.
Applications of electromagnetic waves:
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Communication (radio, television, mobile phones, satellite communication):
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Radio waves: AM radio, FM radio, CB radio.
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Microwaves: microwave ovens, radar.
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Infrared radiation: TV remote controls, night vision goggles. -Visible light: optical fiber communication.
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Ultraviolet radiation: germicidal lamps, sunlamps. -X-rays: medical imaging, security screening, baggage screening. -Gamma rays: cancer treatment, medical imaging.
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Remote sensing (weather forecasting, Earth observation): Remote sensing is the use of electromagnetic waves to collect data about an object or area from a distance.
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Medical imaging (X-rays, MRI, CT scans):
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X-rays: medical imaging, security screening, baggage screening.
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Magnetic Resonance Imaging (MRI): uses strong magnetic fields and radio waves to produce detailed images of the inside of the body.
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Computed tomography (CT): produces cross-sectional images of the body by combining a series of X-ray images.
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Heating (microwave ovens, infrared lamps):
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Microwave ovens: use microwaves to heat food. -Infrared lamps: are used to provide heat, such as in heat lamps and infrared saunas.
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Industrial processes (welding, cutting, curing):
- Microwaves: welding and cutting metals.
- Ultraviolet radiation: curing inks, paints, and adhesives.