Can someone help me with what length lights I need for my fence please?

[Whatisthename]

I have a 15 foot fence and a 30 foot fence. I’m ordering some solar panel lights, little globe ones but I can’t work out what length I need? I want to be able to do a sight ‘scallop’ effect, dip down slightly maybe 3/4 times across the 15 foot one? Not loads, just slightly so it’s not straight across? What do you think I would need?

I’m looking at 23 foot for the 15 foot fence? That would be enough wouldn’t it? What about the 30 foot??

Tia