In the 3rd edition, on page 118, the projection operator is introduced as


Then Griffiths says that when $\hat{P}$ acts on another vector, it looks like this:


I'm having trouble understanding why it looks like above and not like this:


  • 4
    $\begingroup$ It's the same. It's just multiplication of a vector by a number. $\endgroup$ – Javier Apr 21 at 5:00
  • $\begingroup$ Oh right, the inner product is just a number. Thanks! $\endgroup$ – NoThangButtaChknWang Apr 21 at 5:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.