I did A-level physics just because it was the "thing to do" if I was going to do A-level maths & chemistry. I was lucky enough to have a very gifted A-level physics teacher, Eric Green, who made what can be a dry subject very very interesting indeed. With the interest came the want, no, the need to know why and from that point on doing A-level physics was actually one of the most enjoyable and rewarding (but not the easiest!) things I've ever done.
---Mik