Definition of Spectrum

The spectrum refers to the band of colors or wavelengths obtained when light is dispersed through a prism or diffraction grating.

Types of Spectrum

• Continuous Spectrum
  • Contains all wavelengths without any gaps.
  • Example: Sunlight, which gives a rainbow of colors (red to violet).

• Emission Spectrum
  • Produced by a hot gas or excited atoms.
  • Appears as bright lines on a dark background.
  • Example: Hydrogen emission spectrum.

• Absorption Spectrum
  • Produced when light passes through a cooler gas or medium.
  • Appears as dark lines on a continuous spectrum background.
  • Example: Solar spectrum.

Formation of Spectrum

• Dispersion of Light:
  When light passes through a prism, it splits into its constituent colors due to differences in the bending (refraction) of each wavelength.
  Order of Colors (VIBGYOR): Violet, Indigo, Blue, Green, Yellow, Orange, Red.

• Diffraction Grating:
  A device used to separate light into its components more precisely using the principle of diffraction.

Important Terms

• Wavelength (λ): The distance between two consecutive peaks or troughs in a wave.
• Frequency (f): The number of wave cycles passing a point per second.
• Energy (E): Related to wavelength and frequency (E=hf, where h is Planck’s constant).

Applications of Spectrum

• Astronomy:
  • Study of stars and planets using absorption and emission spectra.
  • Identification of elements in celestial bodies.

• Spectroscopy:
  • Analysis of chemical substances by studying their spectra.

• Communication:
  • Use of electromagnetic spectrum (radio waves, microwaves) in telecommunication.

• Medical:
  • X-rays (part of the spectrum) are used in diagnostics.

Electromagnetic Spectrum

• A broader classification of waves includes visible light, radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.

• Order of Wavelength:
  Radio waves > Microwaves > Infrared > Visible Light > Ultraviolet > X-rays > Gamma rays.

Characteristics of Light Spectrum

• Dispersion: Separation of light into its components.

• Refraction: Bending of light when passing from one medium to another.

• Diffraction: Spreading of light when it encounters an obstacle or slit.

Newton’s Experiment

• Newton demonstrated the dispersion of white light into its constituent colors using a prism, proving that light is a mixture of colors.

Significance in Science

• Provides insights into the composition, temperature, and motion of celestial objects.
• Helps in understanding the wave-particle duality of light.