When Mendel crossed a Tall plant with a dwarf plant, no medium height plants were obtained in F1 generation. Why?

When Mendel crossed a Tall plant with a dwarf plant, no medium height

1.	When Mendel crossed a Tall plant with a dwarf plant, no medium height plants were obtained in F1 generation. Why?
Answer» When Mendel crossed a Tall plant with a dwarf plant, no medium height plants were obtained in $F_{1}$ generation. Why?