A beta particle and an alpha particle are projected into a circular trajectory at the same time in the same direction, each moving in a constant speed. The beta particle goes all the way round and then collides with the alpha particle. On collision, the beta particle is repelled and moves in the opposite direction. Once again, they collide at the starting point, when the alpha particle has completed one round. Find the ratio of the speed of the beta particle to the alpha particle. (Assume that the speed of both the particles throughout the course remains constant).

1) √2 – 1 : 1
2) 3 : √2
3) 3 : 1
4) √2 + 1 : 1
5) √2 + 1 : √2 – 1