Fundamentals of light

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  1. Fundamentals of light 
  2. Nature of light and introduction to light fundamentals
  3. Luminous body Vs. Illuminated body
  1. What is the frequency of red light, λ\lambda = 635nm?
    1. Calculate the distance covered by light in feet for 1ns.
        1. What is the length of green light that lasts for 4.0 fs?
        2. How many wavelengths of green light (λ\lambda = 550 nm) are included in such a pulse?
        1. Calculate the distance from Earth to the moon knowing that a pulse of light sent to the moon takes 2.562s to return back to Earth.
          1. Light takes 16 minutes to cross Earth's orbit (3.0× 1011m). calculate the speed of light
            1. What is the illumination on a wall if it is lighted by 1750-lm light bulb which is 1.50 m away from the wall?
              1. A lamp is moved from 40cm to 80cm above the pages of a book. What is the illumination before and after the lam is moved?
                1. The illumination on desktop is 3.0 × 102lx. The source providing the illumination is 2.0m above the desk. What is the intensity (luminous flux) of the lamp?
                  Topic Notes

                  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