From what I've read, the intensity of sunlight that reaches the Earth's surface is about 1 kW/m², or 100 mW/cm². For instance, a 500 mW laser would supposedly have the same burning power as a ~2.5 cm convex lens.
But one thing I've noticed is that laser light seems to burn better than focused sunlight at the same power. Case in point, I have a 6 cm magnifying glass (which would focus π * (6 / 2)² ≈ 28.3 cm² = 2.83 W of sunlight) that could barely ignite newspaper except maybe on a very sunny day. In comparison, even 500 mW lasers seem to easily light things on fire.
I know sunlight and laser light are very different, but what makes lasers so "good" at burning things? For example, does coherent light transfer energy more efficiently than sunlight? The only thing I could think of is the difference in irradiance; for example, my 6 cm lens can hardly get the dot to below 4 mm while a laser beam could be easily focused down to below 1 mm. Am I missing any others?
But one thing I've noticed is that laser light seems to burn better than focused sunlight at the same power. Case in point, I have a 6 cm magnifying glass (which would focus π * (6 / 2)² ≈ 28.3 cm² = 2.83 W of sunlight) that could barely ignite newspaper except maybe on a very sunny day. In comparison, even 500 mW lasers seem to easily light things on fire.
I know sunlight and laser light are very different, but what makes lasers so "good" at burning things? For example, does coherent light transfer energy more efficiently than sunlight? The only thing I could think of is the difference in irradiance; for example, my 6 cm lens can hardly get the dot to below 4 mm while a laser beam could be easily focused down to below 1 mm. Am I missing any others?
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