Draw ray diagrams of convex lens when the position of the object is at infinity.

Draw a ray diagrams of convex lens when the position of the object is at $2 {\mathrm{F}}_1$.

Draw a ray diagrams of convex lens when the position of the object is between ${\mathrm{F}}_1$ and $2{\mathrm{F}}_1$.

With the help of a ray diagram, explain the following terms: focus of a convex lens