How many photons with a wavelength of 625 nm is needed to heat a 225 g block of ice?
What is the power needed to heat it in 25 seconds?
What is the power needed to heat it in 25 seconds?
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Are we assuming that you're merely melting the block of ice, and nothing more? If so, then:
Q = Hf * m
Hf = heat of fusion = 334 J/g for ice
m = mass
Q = 334 * 225 = 75200 J
You need 75200 J to melt the ice.
Find the energy of the photon:
E = hc/w = 6.626E-34 * 3E8 / 625E-9 = 3.18E-19 J/photon
75200 J (1 photon / 3.18E-19 J) = 2.36E23 photons needed.
You need a total of 2.36E23 photons, so 2.36E23 photons / 25 seconds = 9.45E21 photons/s.
Each photon has an energy of 3.18E-19, so:
9.45E21 photons (3.18E-19 J/photon) = 3000 J/s
Q = Hf * m
Hf = heat of fusion = 334 J/g for ice
m = mass
Q = 334 * 225 = 75200 J
You need 75200 J to melt the ice.
Find the energy of the photon:
E = hc/w = 6.626E-34 * 3E8 / 625E-9 = 3.18E-19 J/photon
75200 J (1 photon / 3.18E-19 J) = 2.36E23 photons needed.
You need a total of 2.36E23 photons, so 2.36E23 photons / 25 seconds = 9.45E21 photons/s.
Each photon has an energy of 3.18E-19, so:
9.45E21 photons (3.18E-19 J/photon) = 3000 J/s