Concept Of Waves And Electromagnetic Waves

Concepts to remember for JEE and CBSE board exams on the of Waves and Electromagnetic Waves

Wave motion:

  • Characteristics of waves:

  • Wavelength: the distance between two consecutive troughs or crests of a wave.

  • Frequency: the number of waves passing a fixed point in one second.

  • Amplitude: the maximum displacement of a particle from the equilibrium position.

  • Wave velocity: the speed at which a wave travels through a medium.

  • Transverse and longitudinal waves:

  • Transverse waves: the particles of the medium vibrate perpendicular to the direction of propagation of the wave.

  • Longitudinal waves: the particles of the medium vibrate parallel to the direction of propagation of the wave.

  • Simple harmonic motion: a periodic motion where the restoring force is directly proportional to the negative displacement from the equilibrium position.

  • 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.

  • 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.

  • Standing waves: Formed when two progressive waves of the same frequency and amplitude travel in opposite directions and interfere with each other.

  • The process by which energy is built up in a vibrating system is called resonance.


Electromagnetic waves:

  • Properties of electromagnetic waves:

  • Speed of light: (c = 3.00 \times 10^8) m/s.

  • Frequency range: from (10^0 ) Hz to (10^{26}) Hz.

  • Wavelength range: from (10^8 ) m to (10^{-12}) m.

  • 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)

  • Generation and detection of electromagnetic waves:

  • Electromagnetic waves are generated by charged particles undergoing acceleration.

  • Electromagnetic waves are detected by devices that respond to their oscillating electric and magnetic fields.

  • Polarization of electromagnetic waves:

  • For a transverse wave, the direction of oscillation of the electric field vector is called the polarization of the wave.


Applications of electromagnetic waves:

  • Communication (radio, television, mobile phones, satellite communication):

  • Radio waves: AM radio, FM radio, CB radio.

  • Microwaves: microwave ovens, radar.

  • Infrared radiation: TV remote controls, night vision goggles. -Visible light: optical fiber communication.

  • Ultraviolet radiation: germicidal lamps, sunlamps. -X-rays: medical imaging, security screening, baggage screening. -Gamma rays: cancer treatment, medical imaging.

  • 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.

  • Medical imaging (X-rays, MRI, CT scans):

  • X-rays: medical imaging, security screening, baggage screening.

  • Magnetic Resonance Imaging (MRI): uses strong magnetic fields and radio waves to produce detailed images of the inside of the body.

  • Computed tomography (CT): produces cross-sectional images of the body by combining a series of X-ray images.

  • Heating (microwave ovens, infrared lamps):

  • Microwave ovens: use microwaves to heat food. -Infrared lamps: are used to provide heat, such as in heat lamps and infrared saunas.

  • Industrial processes (welding, cutting, curing):

    • Microwaves: welding and cutting metals.
    • Ultraviolet radiation: curing inks, paints, and adhesives.