Determining the number of photons that reach the earth

In summary, the number of photons per second per square meter that reach the earth is 3.066x10^21, assuming a light intensity of 910 W/m2 and a wavelength of 668 nm for all photons. This is calculated using the equation P/A = (910)*(668x10^-9)/(6.63x10^-34)(3x10^-8).
  • #1
phys62
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Homework Statement


Light is shining perpendicularly on the surface of the Earth with an intensity of 910 W/m2. Assuming all the photons in the light have the same wavelength (in vacuum) of 668 nm, determine the number of photons per second per square meter that reach the earth.



Homework Equations


The power per area is:
P/A = (# of photons /t /A)*(energy / photon)

E/photon = h nu = hc / lambda

photons /t /A = (P/A) * lambda / hc


The Attempt at a Solution


photons /t /A = (P/A) * lambda / hc
photoms /t /A = (910)*(668x10^-9)/(6.63x10^-34)(3x10^-8) = 3.066x10^21
 
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  • #2
Looks good!

Just a small typo, c is 3x10^+8. Looks like you used the correct value for the calculation though.
 
  • #3
The program I enter my homework answers into doesn't let me have that many decimal places in my answer though (we have to write it out long, it doesn't let us put x10^21), so I was assuming I must've done something wrong.. :-/
 
  • #5
Oh wow, I never knew I could write my answers that way on this program. haha thanks!
 

1. How is the number of photons that reach the earth determined?

The number of photons that reach the earth is determined by measuring the amount of solar radiation that reaches the earth's surface. This can be done using instruments such as radiometers and pyranometers, which measure the amount of incoming solar radiation.

2. What factors affect the number of photons that reach the earth?

The number of photons that reach the earth can be affected by various factors, such as atmospheric conditions (such as clouds, air pollution, and water vapor), the earth's distance from the sun, and the sun's activity (such as solar flares and sunspots).

3. How does the earth's atmosphere impact the number of photons that reach the earth?

The earth's atmosphere plays a crucial role in determining the number of photons that reach the earth. It acts as a filter, absorbing and scattering some of the incoming solar radiation. The amount of photon absorption and scattering depends on the composition and thickness of the atmosphere at a particular location.

4. Can we measure the number of photons that reach the earth from space?

Yes, we can measure the number of photons that reach the earth from space using satellites equipped with sensors that can detect solar radiation. These satellites provide a more comprehensive and accurate measurement of the amount of solar radiation reaching the earth.

5. How is the number of photons that reach the earth related to climate change?

The number of photons that reach the earth plays a significant role in the earth's climate. Changes in the earth's distance from the sun, as well as changes in the sun's activity, can affect the amount of solar radiation reaching the earth, which can, in turn, impact the earth's temperature and climate patterns.

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