prep 3 unit 2 ; lesson 2 part 2/3 Formation of images through lenses
Channel: Mr. Emad Science channel
Date: 06/01/2021

#شرح دروس science للمرحله والاعداديه
 # The image formed by the convex lens:
To study the cases of the formation of the image by using the convex lens we will use three rules to determine 
the direction of the light ray after passing 
through the lens.
1-The incident light ray passing through 
    the optical Centre of the lens,     
    It continues to pass inside the lens
    and passes without refraction.

2-The incident light ray parallel to the principal axis, 
   it exits the lens passing through the focus

3-The incident light ray passing through the focus, 
      # it exits the lens parallel to the principal axis
The cases of the formation of the images by the convex lens (collective):To determine the position and characteristics of the formed image by the convex lens, follow the following steps:1-Use the protractor and draw the convex lens2-Draw the principal axis of the lens (it is a straight line    passing by the focus and the optical centre of the lens).3-Determine on it the position of the focus (f) and twice   the focal length (c) on the principal both  sides of the lens.4-Draw a ray coming from the highest point of the object     so it falls parallel to the principal axis  thus refracts      and leaves the lens and passes through the focus
5-Draw a ray from the same point passing by the optical centre of the lens thus leaves with no refraction.
6-To determine the position when two respected of the two penetrating rays determines the image of the lit  point.
7-Determine the position and 
characteristics of the images 
formed in the six cases 
shown in the following slides
#1-Very far (the incidence ray are parallel
Real 
Very tiny (dot)
#2-At a distance larger than
the radius of
curvature.
(greater than double of focal length)
Real
Inverted 
Diminished
(smaller than the object
#3-At the distance equal the radius of curvature (At the Centre of curvature
Real 
Inverted
equal to object
4-At distance between focus and Centre of curvature  
Real
Inverted 
Magnified
(larger than object)
5-At the focus
No image is form
Because the extension of the refracted light rays are parallel to each other
6-At distance less than focal length 
(before the focus)
Virtual. Erect
(upright )
Magnified
Second: The concave lens
The focus of the concave lens:
If parallel rays fall on the concave lens, the rays passes through the concave lens and leaves from each other (diverging) as if it is produced from a point in front of the lens and is called 
“The diverging focus of the concave lens” and it is a virtual point (cannot be received on a screen). The lens is also known in this case as the diverging lens because it diverges the rays after they pass through
The image formed by the concave lens:
The image formed by the concave lens is always virtual, smaller and erect.  we used two rays to identify how the image of the object is formed.