Waves: Light

Waves: Light

Properties of Light Waves

  • Light is a form of electromagnetic radiation and can be treated as both a wave and a particle known as a photon.
  • Light waves are transverse waves, which means their oscillations are perpendicular to the direction of energy transfer.
  • The speed of light in a vacuum is approximately 299,792 kilometres per second.

Reflection of Light Waves

  • Reflection occurs when light bounces off a surface.
  • When reflecting off a smooth surface like a mirror, light undergoes specular reflection, creating a clear image.
  • When reflecting off an uneven or rough surface, light undergoes diffuse reflection, scattering the light in multiple directions.

Refraction of Light Waves

  • Refraction occurs when light enters a different medium and changes speed, causing it to change direction.
  • The angle of incidence and the angle of refraction are measured from the normal (a line perpendicular to the surface at the point of incidence).
  • Snell’s Law can be used to calculate the angles of incidence and refraction. It states that the product of the refractive index and the sine of the angle of incidence is equal to the product of the refractive index of the second medium and the sine of the angle of refraction.

Absorption of Light Waves

  • When light waves pass through a substance, they can be absorbed by the substance. This is the reason why objects appear coloured - the colours we see are the wavelengths of light that were not absorbed by the object and instead were reflected into our eyes.

Dispersion of Light Waves

  • Dispersion of light happens when light is separated into its constituent colours. This happens because different wavelengths of light refract at slightly different angles in a prism, for example, creating a rainbow effect.
  • The common mnemonic ‘ROYGBIV’ can be used to remember the colours of light in order of increasing frequency: red, orange, yellow, green, blue, indigo and violet.

The Electromagnetic Spectrum

  • Light is a part of the electromagnetic spectrum and sits between ultraviolet and infrared radiation.
  • The electromagnetic spectrum in order of increasing frequency includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
  • All electromagnetic waves travel at the same speed in a vacuum, but have different wavelengths and frequencies.