Headlight Bulbs

[dunks]

Forgive my ignorance , 🤨🤨🤨🤨🤨 but on any car i've had in the past, the headlights would contain say a h4 bulb which did the main and dipped beam a capless for the sidelight and then maybe say a H1 for the fog , which I presumed was what gave different brightness's and patterns for each light function,  So on the boxster my light unit has a H6 for sidelight but then 3 x H7's each side  , Which i presume is dipped, main and fog ,  So how can switching from dipped main to Full Main with the same type of bulb give a wider through of light on the road , and again how can the fog with the same type of bulb give a longer through of light in the road

[½cwt]

All to do with the lenses, reflectors and projectors.  The bulb is just a more or less point source of light and has no distribution characteristics in itself (although the H4 bulb has a cover over the dipped element to partly shield it) it is the optics do the spreading out or focusing to make the beam patterns that you actually see.