# Thread: How does the distance from a light source effect amount of energy a planet receives?

1. ## How does the distance from a light source effect amount of energy a planet receives? var addthis_config = {"data_track_clickback":false};

If a planet were twice as far from the sun as earth is, would it recieve half as much from sun as earth does? What effect would it have on the planets temperature?

2. I think larger the distance, lower is the temperature of the planet because heat is lost when it travels from sun to planet. lager the distance larger is the heat loss and lower is the planet's temperature.

3. the further you are away from a light source,the less amount of light you recieve. light particles are called photons and the amount of photons you recieve from a source is given by the equation +1/R squared. this basically means that the number of photons detected gets less and less with distance from the light source.

planets that are further away from the Sun are going to be colder than the ones closer to it due to infrared radiation from the sun,in the form of photons, becoming less concentrated with distance from the sun. infrared radiation carries heat energy and it is released when it hits an object,you feel the heat of the sun's infrared radiation on you're skin on a summers day.

even if the sun had no temperature but still released infrared radiation,planets further from it would still be colder than the ones nearer the sun.

to see +1/R squared in action check this out:
http://www.astro.ubc.ca/~scharein/a311/Sim/1overR2/1overR2.html

4. It's the old inverse square law. The energy you receive from sun light varies inversely with the square of the distance. In other words if you double the distance, the amount of energy received is reduced by one fourth.

5. as the distance increase the average energy will decrease , this is due to the fact that the same energy will will cover a wider area

6. Yay, 3 out 4 answered correctly and two even explained why.

I'd generalize even more than that. It doesn't matter what you're talking about - light, gravity, electric charge, paint. If you have a certain amount of something and try to spread it over a larger surface area, there won't be as much per square meter as the surface area increases.

The intensity of just about any energy source decreases inversely proportional to the square of the distance because the formula for surface area is 4(PI)r^2. You're dividing a constant amount of energy by a larger surface area (even if the 4(PI) part is embedded in some other constant, as in the case of gravity).

Edit: It always drives me nuts when people think that energy just disappears in the vacuum of space without providing some explanation for what absorbed that energy while it was en route. No energy disappears - it's just spread out over a larger area.

7. as the distance increases the square of the energy decreases.

An example.

If the distance increases by 2, then the energy decreases by 4. Because 2 x 2 = 4.

the energy is spread over a larger area.
This is because distance and area are directly proportional in this case.

8. Inverse as the square of the distance.

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