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+--- Thread: Light Energy into Heat (/showthread.php?tid=11852)
Light Energy into Heat - Hazzy - 2009-05-31
If I shine 10 units of sunlight through a Magnifying Glass, I get some amount of heat on my target.
How does that heat change if I double the units of sunlight to 20?
Light Energy into Heat - Dusk - 2009-05-31
Hazzy Wrote:If I shine 10 units of sunlight through a Magnifying Glass, I get some amount of heat on my target.
How does that heat change if I double the units of sunlight to 20?
It doubles?
Light Energy into Heat - Flaxative - 2009-05-31
I think it depends. The lense can double the output, x1.5 it, triple it, and that affects the light/heat output. What is the ratio of light to heat for your magnifying glasses lense?
Light Energy into Heat - Veneni - 2009-06-01
Conservation of energy => the energy (heat in this case) doubles.
I fairly sure the glass takes in almost no energy, so that effect can be neglected.
Flaxative you're thinking of energy density. The lens packs the energy into a smaller spot, but it doesn't add energy. It doesn't matter if the target is heated by a ray 1cm² or 10cm², if you wait long enough for the heat to spread the sample will have the same temperature rise.
Light Energy into Heat - JoeTang - 2009-06-01
Hazzy Wrote:If I shine 10 units of sunlight through a Magnifying Glass, I get some amount of heat on my target.
How does that heat change if I double the units of sunlight to 20?
If you shine x Candela through a Magnifying Glass and get y amount of heat transfer, and you repeat with 2x Candela, I believe you get around 2y amount of heat transfer, though it will vary depending on the surface, as well as the initial temperature, and intensity.
For the record, the brightness of light is measured by Intensity, with Candela. 10 units of sunlight has no real meaning. Also, heat is the transfer of energy from one body to another due to a difference of temperature.
Light Energy into Heat - Flaxative - 2009-06-01
Light causes the surface to heat up, and doesn't the lense at least add a little? If you have awide area when you are magnifying, it doesn't heat up as quickly so the short term heat gain is higher.
Light Energy into Heat - Veneni - 2009-06-02
Flaxative Wrote:Light causes the surface to heat up, and doesn't the lense at least add a little? If you have awide area when you are magnifying, it doesn't heat up as quickly so the short term heat gain is higher.
If it were so you could build a machine that uses one lightbulb, makes the light go through thousands of lenzes, till the total energy added is more than the energy needed to power the lamp and you'll have free energy.
Would be funny though to power your house with only one lightbulb
