Linked Questions

2
votes
1answer
8k views

Highest temperature possible to achieve using magnifying glass and sunlight [duplicate]

Temperature of the surface of the sun is about 5750K. Can you heat an object to more than 6000K using magnifying glass and sunlight? According to second law heat cannot be transferred from colder to ...
105
votes
7answers
16k views

Is it possible to start fire using moonlight?

You can start fire by focusing the sunlight using the magnifying glass. I searched the web whether you can do the same using moonlight. And found this and this - the first two in Google search ...
7
votes
1answer
720 views

Can solar furnace achieve higher temperature than sun surface? [duplicate]

Can solar furnace achieve higher temperature than sun surface? I guess not, but I'm not sure about that. Can you check my reasoning: -------- My reasoning ----------- Consider Sun as a black body ...
6
votes
1answer
1k views

Is Randall Munroe's “what-if” xkcd correct that magnified moonlight can't get things hotter than the moon? [duplicate]

Note: I am NOT asking if moonlight can be used to start a fire. I am asking whether these particular arguments in support of the claim that it cannot are correct. i.e. I'm looking for an answer that ...
5
votes
1answer
705 views

Second Law of Thermodynamics…confusion over an example

By the second law of thermodynamics, you shouldn't be able to use any amount of mirrors/lenses to focus sunlight onto an object and heat it past the surface temperature of the sun (approximately 5800K)...
9
votes
2answers
866 views

Conservation of energy when focusing black body radiation on another black body

This question about whether or not it is possible to focus black-body radiation to make something hotter than the radiation's source was answered mostly negative: the second law of thermodynamics and/...
1
vote
3answers
797 views

Temperature increase from focusing light using a lens. (Equations required)

Could someone please quote and explain the Equations required that I would need to calculate the temperature increase of an object with a lens focussing the light from a celestial body. Therefore ...
3
votes
1answer
917 views

Can you use sun light to heat an objects surface to hotter than the surface of the Sun? [closed]

I was reading this question: Concentrating Sunlight to initiate fusion reaction and some of the comments, as well as an answer, suggest that thermodynamics second law prevents what I ask in the title. ...
1
vote
4answers
101 views

Laser beam focus

Why isn't it possible to focus a laser beam to an infinitely small point in space? I am familiar with the shape of a gaussian beam, but why can't my $w_0$ be equal to zero?
3
votes
1answer
132 views

Solar Power Fusion

Would it be possible through a clever arrangement of solar dishes, lenses and mirrors etc, to create fusion at the focal point? Imagine you arrange your solar dishes, lenses and mirrors in such a way,...
1
vote
0answers
87 views

Simple thermodynamic proof that light from a source cannot be focused to heat an object above the source's temperature

I was thinking about the question in the title. I found the following thread, and some of the answers are making my head spin! Is it possible to focus the radiation from a black body to make ...
2
votes
0answers
77 views

Lens-Mirror systems and conservation of specific intensity

This came out of a discussion I started yesterday and a related discussion I found. I'll recap the problem quickly: Consider two blackbodies, with surface areas $A_1$ and $A_2$ and temperatures $T_1$ ...