Burning Bushes: The Science Behind Water Droplets and Fire Ignition

In summary, it is said that bush fires in Africa can be started by water droplets in the grass. The lens (or water drop) concentrates the light that enters it, at its focal point, which is how some old weather-recording devices worked. Even if I were, a water droplet in nature is so grossly deformed apart from an ideal lens that the potential is even much less, it seems to me.
  • #1
jollytime
2
0
It is said that bush fires in Africa can be started by water droplets in the grass. How could this work? What actually causes the burning?
 
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  • #2
Have you ever used a magnifying glass in the sunlight to light fires?
 
  • #3
yes, but i never knew how that worked..
 
  • #4
The lens (or water drop) concentrates the light that enters it, at its focal point.
 
  • #5
This is how some old weather-recording devices worked- a large glass ball sat in the center of a ring of paper. If the sun was out, the paper would have a char line, and if it was cloudy, there would be no line.
 
  • #6
Andy Resnick said:
This is how some old weather-recording devices worked- a large glass ball sat in the center of a ring of paper. If the sun was out, the paper would have a char line, and if it was cloudy, there would be no line.

OK, and I'm not trying to be silly here at all, but I question the water droplet scenario.

A water droplet tends to be quite small, and I would imagine also grossly distorts while clinging to, say, a blade of grass or some such thing.

It seems to me that the droplets size itself, even if it could be shaped into an ideal lens for starting a fire, would simply be inadequate. After all, with a true lens the size of a water droplet, I tend to doubt there is enough surface area to concentrate sufficient sun-light to start a fire. Indeed, could a fire be started with a lens which has a diameter less than that of a pencil eraser?

But I could be wrong on that aspect.
Even if I were, a water droplet in nature is so grossly deformed apart from an ideal lens that the potential is even much less, it seems to me.

Just my thoughts...
 

What is the relationship between water droplets and optics?

The presence of water droplets in the air can affect the behavior of light, leading to various optical phenomena such as rainbows, halos, and glories. This is because the water droplets act as tiny prisms that bend and reflect light in different ways.

How do water droplets create rainbows?

When sunlight passes through a water droplet, it is refracted, or bent, as it enters the droplet and then again as it exits. This causes the light to separate into its component colors, creating a rainbow.

What causes halos and glories to form around the sun or moon?

Halos and glories are formed when light is reflected and refracted by water droplets in the atmosphere, such as those found in clouds. The droplets act as tiny prisms, separating the light and creating the appearance of a halo or glory around the light source.

Can water droplets affect the way we see objects?

Yes, water droplets can cause objects to appear distorted or magnified when viewed through them. This is due to the refraction of light as it passes through the droplets.

How do water droplets on a surface affect the reflection of light?

When light hits a smooth surface with water droplets on it, some of the light is reflected off the surface while some is refracted by the droplets. This can create a distorted or blurred reflection, depending on the size and shape of the droplets.

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