General information on the entry process for all NST Part III subjects can be found here.
The entry requirements for Part III Physics are published in the Reporter.
Students taking Part II Physics (or Part II Physical Sciences Half Subject Physics) will be asked during Lent Term to provide a provisional indication as to whether or not they intend to continue to Part III Physics. Following publication of examination results in Easter Term, you will be notified whether you have been offered a place on Part III Physics. You should not proceed to the B.A. degree after Part II if you are intending to continue to Part III Physics; on successful completion of the M.Sci., you will also be awarded the B.A. degree.
Students from other Triposes, and those who do not achieve these entry requirements, must follow the process as advertised in this article.
If you do not achieve the requirements for entry to Part III Physics you should discuss your options with your DoS and Tutor. The procedure detailed in the Reporter (scroll down to the bottom of the page to “Consideration of special cases“) explains how you may apply to be considered as a special case. The pro forma mentioned in the Reporter entry can be found on the Faculty of Physics and Chemistry web page, see the link “Pt II/III progression form (for use by colleges)”.