Lens hoods are primarily designed to avoid unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, since the end of the lens is extended, you also get the added benefit of some extra protection from accidental impact.
Dedicated lens hoods are designed to match the specific focal length of the lens it was designed for.
JJC LH-J61C replaces OLYMPUS Lens Hood LH-61C
l OLYMPUS ZUIKO DIGITAL ED 14-42mm 1:3.5-5.6
l OLYMPUS M.ZUIKO DIGITAL ED 14–150mm 1:4.0–5.6