To construct a ray diagram we use two light rays which are so chosen that it is easy to know their directions after refraction from the lens. List these two rays and state the path of these rays after refraction. Use these two rays to locate the image of an object placed between ‘f’ and ‘2f’ of a convex lens.

To construct a ray diagram for a lens, we commonly use the following two rays:

1. Ray parallel to the principal axis: A ray of light parallel to the principal axis, after refraction through a convex lens, passes through the principal focus ($F_2$) on the other side of the lens.
2. Ray passing through the optical centre: A ray of light passing through the optical centre ($O$) of a convex lens emerges without suffering any deviation.

Image Location for Object between $F_1$ and $2F_1$:

When an object is placed between $F_1$ and $2F_1$ of a convex lens, the two rays intersect on the other side of the lens beyond $2F_2$.

• Position of Image: Beyond $2F_2$
• Nature of Image: Real and inverted
• Size of Image: Magnified (larger than the object)