page 26 q1chemical bonding module and how is there no hybridization in nh3

In NH3 there is hybridization i.e. sp3 having Tetrahydral gemotry and pyramidal shape But in PH3 there is no hybridization because the s orbital is stereochemically inactive i.e. it is not involved in hybrization. Only pure p orbitals involve in hybridization giving bond angle close to 90.