Solution
The bottle has a greater curvature than the magnifying glass and therefore has a shorter focal length. The shorter focal length means that light is focused onto dry leaves resting near the bottle.
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Solution
The bottle has a greater curvature than the magnifying glass and therefore has a shorter focal length. The shorter focal length means that light is focused onto dry leaves resting near the bottle.
Click to hide the solution
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Bushfires
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Light is focused by glass bottles in much the same way as a magnifying glass. Bushfires can often be started by discarded bottles on clear sunny day. The Australian forest is full of fuel (eucalyptus oil) and fires start with. Once a fire has started it is fuelled by the oil in the gum trees. | |
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It is more likley that the bottle filled with water will start a bushfire than the magnifying glass next to it. Why? Click for solution. |
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