Simplify the following text for a Grade 4 native English-speaking person.
Original: Since 1992 , the Australian Institute of Physics has awarded the Bragg Gold Medal for Excellence in Physics to commemorate Sir Lawrence Bragg ( in front on the medal ) and his father , Sir William Bragg , for the best PhD thesis by a student at an Australian university .
Simplified: Bragg was always known as Sir Lawrence Bragg , and his father was Sir William Bragg .