Size of light reflector dome- does it matter?

[DivergentKyle]

I'm wondering if my dome fixture would be considered small. My dome size isn't technically incorrect- it is for a 100 watt bulb which is what I use. Yet, we also have a turtle in our household that we are currently babysitting who also uses a 100 watt, except this done is larger and can hold a bulb up to 160 watts. Here is a photo of the two domes in case that would be somewhat helpful to see.



Does size of the dome reflector matter? Does a bigger dome mean a better expansion of light or is the only thing that makes the real difference the wattage and not the dome?

 

[Taterbug]

The bigger dome will project a bigger patch of light and heat. The smaller done would be ok if the hot spot it makes isn't too small - you want it at least the size of your dragons body with no extra intense spots.

 

[jarich]

The dome also influences how much heat is trapped around the fixture. Since all halogens are made with reflectors inside the back of the bulb itself, the dome wont make any difference to the spread of light, rather the trapping of heat. With a larger dome, the heat is trapped in a less constrained way, so you are able to have a higher wattage bulb. (the largest domes often have larger wiring also) If you tried to stick a 160 watt light in your smaller dome, you could start a fire or melt the wiring cord plastic. So its very important not to go above the recommended wattage rating.