Fundamentals of light - Light

Fundamentals of light



In this lesson, we will learn:

  • What is light?
  • Source of light
  • Light is the visible part of electromagnetic waves
  • Light range frequencies
  • Visible light colors and wavelengths
  • Ray model of light
  • Solving problems involving the speed of light
  • Solving illumination problems


Introduction to Light Fundamentals
  • Light is emitted and reflected from objects around us
  • Light is a small visible part of electromagnetic waves.
  • Light travel along straight line in vacuum or other uniform medium
  • The nature of light is explained by two models; particle model and wave model
  • Light frequency changes upon moving along the electromagnetic spectrum
  • Light is the range of frequencies of electromagnetic waves
  • Light waves have wavelength about 400nm to 700nm
  • Shortest wavelengths are seen as violet light
  • Longest wavelengths are seen as red light
  • Knowing that light travels along a straight line in vacuum or any uniform medium leads us to the ray model of light.
  • A ray of light is a straight line representing the path of a narrow beam of light.

Waves in two dimensions

Speed of Light
  • Speed of light is represented by letter cc
  • Speed of light is constant in the air and is 3.00×108m/s
  • Recall the equation V=λfV=\lambda f to find the speed of waves, we can modify the equation in terms of speed of light c=λfc=\lambda f

Luminous body Vs. Illuminated body
  • Luminous body emits light waves (sun, lamp)
  • Illuminated body reflects waves produced by an outside source (moon, bridge)
  • Luminous flux, is the rate at which light is emitted from a source
  • Unit of luminous flux is the lumen
  • The mount of illumination of a surface called illuminance,

      • E=E = lumens per square meter =lm/m2= lm/m^{2} OR lux, lx
        E=P4πd2 E = \frac{P}{4 \pi d^{2}}
        P=P = luminous flux of the source
        d=d = distance between the surface and the source
  • Intro Lesson
    Fundamentals of light 
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Fundamentals of light

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