Why was Mendel fairly certain that he had a pure- bred variety when he collected seeds from a pea plant?

What are the components which produce round seed in Mendel's pea plant?

In one of his experiments with pea plants Mendel observed that when a pure tall pea plant is crossed with a pure dwarf pea plant, in the first generation, F_(1) only tall plants appeared. (i) What happens to the traits of the dwarf plants in this case? (ii) When the F_(1) generation plants were self-fertilised, he observed that in the plants of second generation, F_(2) both tall plants and dwarf plants were present. Why it happened? Explain briefly.

What are the components which produce wrinkled seed in Mendel's pea plant?

In order to ensure that he had pure-breeding plants for his experiments, Mendel :

A pea plant pure for yellow seed colour is crossed with a pea plant pure for green seed colour. In F_(1) generation all pea plants were with yellow seeds. Which law of Mendel is applicable?