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SOME IMPORTANT CHARACTERISTICS OF A WAVE
A wave is a sort of disturbance which originates from some vibrating source and travels outward as a continuous sequence of alternating crests and troughs. Every wave has five important characteristics, namely, wavelength (λ), frequency (v), velocity (c), wave number(v ¯ ) and amplitude (a).
Electronic Magnetic Radiation:
Ordinary light rays, X–rays,λ–rays, etc. are called electromagnetic radiations because similar waves can be produced by moving a charged body in a magnetic field or a magnet in an electric field. These radiations have wave characteristics and do not require any medium for their propagation.
- Wavelength (λ): The distance between two neighbouring troughs or crests is known as wavelength. It is denoted by l and is expressed in cm, m, nanometers (1 nm =10–9 m) or Angstrom (1 Å=10–10 m).
- Frequency (v): The frequency of a wave is the number of times a wave passes through a given point in a medium in one second. It is denoted by n(nu) and is expressed in cycles per second (cps) or hertz (Hz) 1Hz = 1cps.
The frequency of a wave is inversely proportional to its wave length (λ)
v ∝ 1 / λ or v = c / λ
- Velocity: The distance travelled by the wave in one second is called its velocity. It is denoted by c and is expressed in cm sec–1.
c = vλ or λ = c / v
- Wave number ( v- ): It is defined as number of wavelengths per cm. It is denoted by v- and is expressed in cm–1.
v- = 1 / λ or v- = v / c
- Amplitude: It is the height of the crest or depth of the trough of a wave and is denoted by a. It determines the intensity or brightness of the beam of light.
- Electromagnetic Spectrum: The arrangement of the various types of electromagnetic radiation in order of increasing or decreasing wavelengths or frequencies is known as electromagnetic spectrum.