Week 2, 3, 4 Achieve Question 4

[205992763]

Hi! I'm struggling with this question, if someone could help me out that would be greatly appreciated.

A liquid is exposed to infrared radiation with a wavelength of 9.44 * 10^-4 cm. Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 44.00 J of heat?

Thank you!!

[Hao Tam Tran 3H]

Hi!

For this question, we have to consider the equations E = hv, which gives the energy of a photon. This can also be written as E = hc/lambda, so we can use this to find a the energy of a single photon in light with the wavelength of 9.44 * 10^-4 cm, or 9.44 * 10^-6 m. Thus, E = (6.626 x 10^-34 J•s)(3 x 10^8 m/s)/(9.44 x 10^-6 m) = 2.11 x 10^-20 J. Since this is the energy of a single photon, we can just take the total energy of 44.00 J and divide it by this, so (44.00 J) / (2.11 x 10^-20 J) = 2.090 x 10^21 photons are needed. Hope that helped!