Introduction

Description de l'image

A diagram of the electromagnetic spectrum


1- Principles and Laws of Geometrical Optics

What is physical optics?

Physical optics is a branch of optics that focuses on phenomena related to the wave nature of light.

What is geometric optics?

Geometric optics is the branch of optics dedicated to the study of light propagation. It primarily focuses on phenomena that are perceptible to the human eye, particularly within the visible spectrum.

2- Light propagation

     In a vacuum

Light travels in a straight line in a vacuum and in transparent, homogeneous media: this phenomenon is called the rectilinear propagation of light.

The speed of light propagation in a vacuum, known as the speed of light (denoted as c), is a universal constant.

Its value is  = 299 792 458 m·s-1

or approximately c = 3,00 × 108 m·s-1.

 C = λ0 ν 








    
λ0
        : wavelength in a vacuum
    


    

        ν
        : frequency
    





     In a vacuum




The speed of light in a material medium is generally less than its speed in a vacuum due to the interaction of light with
    the atoms and molecules of the material. 




 V= λ.ν 







    
λ :
            wavelength
            in a medium
            
        
    





    


    





    
    

        
    

    
 V= C/n

    
C
        : speed of light in vacuum

    


    

        n
        : refractive index of the medium
    

    








    

        
            

                Medium
                air
                water
                glass
                polyster
                Diamond
            

            

                Index n
                1.0003
                1.33
                1.5-1.8
                1.57
                2.42
            

        
    


    

        TABLE 1.1: Some Refractive Indices. 
    




    
    
  • 

            Transparent: A medium is transparent when light can pass through it without being significantly absorbed.
    
    • 
    
  • Homogeneous: A medium is homogeneous when it exhibits uniform characteristics throughout its entire volume. 
    • 
    
  • Isotropic: A medium whose optical properties are identical in all directions is called an isotropic medium. 
    • 



    




3- Law of Reflection
42





3-1- First law of reflection
The angle of reflection is equal to the angle of incidence. Mathematically, it is formulated as follows
i1 = i2 
          i1: is the angle of incidence (the angle between the incident ray and the normal to the surface),
          i2 : is the angle of reflection (the angle between the reflected ray and the normal).
3-2- Second law of reflection
The incident ray, the reflected ray, and the normal to the surface all lie in the same plane.

4- Law of Refraction
43

4-1- First law of refraction
The relationship between the angle of incidence and the angle of
refraction is given by:
n1 sin i1 = n2 sin i2
          i1: is the angle of incidence,
          i2 : is the angle of refraction.
          n1 ,n2,  : is the angle of refraction

4-2- Second law of refraction
At the interface between
two media, the
incident ray, the refracted ray, and the normal to the interface all lie in the
same plane .
4-3- Second law of refraction The limits of recraction
44
The light encounters a less refractive medium, and the refracted
ray deviates from the normal.



The light encounters a more refractive medium, and the refracted
ray moves closer to the normal.



    

Last modified: Wednesday, 22 October 2025, 9:54 PM