# A surprising operator

1. Apr 26, 2009

### asifmumtaz

im studing orthogonalized plane wave method(OPW) IN SOLID STATE PHYSICS. during derivation ,i have difficulty.my question is , is a KET-BRA notation acts like an operator? i.e. Ia><bI .plz help

2. Apr 26, 2009

### Fredrik

Staff Emeritus
Yes, |a><b| is defined by |a><b| (|u>)= |a>(<b|u>).

3. Apr 26, 2009

### JohnSimpson

If you like to think geometrically, this operator takes the projection of your vector |u> onto the vector |b>, which is just some number, and then creates a vector in the |a> direction scaled by this amount.