Inverse Square Law: Calculating Intensity at Different Distances

In summary, the conversation discusses two problems related to intensity and distance from a source. The first problem involves finding the intensity at a distance of 1m from a source with a known intensity at 2km away. The second problem involves finding the reading on a light meter when the distance from a candle is changed. The conversation also mentions using the inverse square law equation and struggling with fractions in solving the problems.
  • #1
emtis
1
0

Homework Statement


Problem One: Two kilometres away from a point source of infrared waves, the intensity is 4 Mw−2. Calculate the intensity 1m away from the source.

Problem two: Light from a candle has an intensity of 20.0 units when a meter is placed 3.0m away. What is the reading on the light meter when it is brought to 1.0 m away?


Homework Equations


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The Attempt at a Solution


Yeah, about that. I'm not really sure where to start. I mean, I have the answers with me, and I think I am able to fill in the values for the inverse square law, but I don't know how to manipulate the equation with fractions to get the answer that I want. I always struggle here, because I ****ing hate fractions and I can't seem to get one thing write with them. I'd like to see the solution with respect to the given formula above please.
 
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  • #2
Look at the first problem. You are given the intensity and distance for one measurement; let those be ##I_1## and ##d_1## respectively. You are also given another distance, and you want to find the intensity at that spot; let those be ##d_2## and ##I_2##. You have to solve the equation you have above for ##I_2##, and then plug in the numbers you have to get your answer.
 
  • #3
If your problem is with fractions than I think you should go back to basics and solve many more fraction problems from some introductory text that includes lots of examples and exercises.
 

Related to Inverse Square Law: Calculating Intensity at Different Distances

What is the Inverse Square Law?

The Inverse Square Law is a principle that states the intensity of a physical quantity, such as light, sound, or gravitational force, is inversely proportional to the square of the distance from the source.

What does "inverse square" mean?

"Inverse square" refers to the relationship between the intensity of a physical quantity and the distance from the source. This means that as the distance from the source increases, the intensity decreases by the square of that distance.

What are some examples of the Inverse Square Law?

Some examples of the Inverse Square Law include the brightness of a light bulb, the loudness of a sound, and the strength of gravitational force.

How is the Inverse Square Law used in physics?

The Inverse Square Law is a fundamental principle in physics and is used to describe the relationship between various physical quantities and their distance from the source. It is particularly useful in fields such as optics, acoustics, and astronomy.

Why is the Inverse Square Law important?

The Inverse Square Law is important because it helps us understand and predict the behavior of physical quantities in various situations. It also allows us to make accurate measurements and calculations in fields such as astronomy, where distances can be vast and the Inverse Square Law plays a crucial role in determining the intensity of light and other phenomena.

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