The document explains how to draw a ray diagram for optical lenses by directing a ray from the object to the image tip, intersecting the principal axis at the lens center. It describes identifying the principal focus beyond the lens and finding the focal length. This method provides a clear position of the lens center and its focal properties.

1. PAPER-4-CONSTRUCTION: WORKSHEET: 3.20.1
1
HINT Draw a ray starting from the tip of the object to the tip of the image.
EXPLANATION:
• This is because one of the rules for drawing the ray diagram is that one line passes from the tip of
the object to the tip of the image and it cuts the principle axis at the centre of the lens. This way,
you are able to get the position of the centre of the lens.
• Also the point beyond the lens where the ray cuts the principle axis is the principle focus. Hence
you get the distance between this point and the centre of the lens as the focal length of the
length.
MS