Light scanning apparatus and image forming apparatus

A light scanning apparatus comprising:

• a deflecting unit configured to deflect a light flux from a light source so that a scanned surface is scanned with the light flux in a main scanning direction;
• and
• an optical system including a first optical element,
• wherein the first optical element includes:
• a transmissive surface configured to transmit a first light flux deflected by the deflecting unit at a first timing to guide the first light flux to the scanned surface;
• and
• a reflective surface configured to totally reflect a second light flux deflected by the deflecting unit at a second timing different from the first timing to guide the second light flux to a light receiving element,
• wherein the reflective surface is arranged on the same side as the light source with respect to a sub-scanning cross section including an optical axis of the optical system, and
• wherein the following inequality is satisfied:
• 55
• ⁢
• °
• ≤
• α
• ≤
• 75
• ⁢
• °
• where α represents an incident angle of a principal ray of the second light flux to the reflective surface.