Physics in Action: How Distance Impacts Energy


Uncover how distance affects the intensity in electromagnetic communication. Dive into the essential study of signal strength and propagation.



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Welcome to “Distance vs. Intensity in Electromagnetic Communication,” your comprehensive guide to understanding the intricate relationship between distance and signal intensity in the realm of electromagnetic communication. This guide expertly demystifies the principles that govern how electromagnetic waves travel, making this crucial physics aspect accessible and engaging for learners from all backgrounds. Whether you’re a student exploring physics fundamentals, a communication technology professional, or just someone curious, this resource aims to boost your understanding and appreciation of electromagnetic signal dynamics.

Embark on Your Scientific Exploration

Dive into the fascinating world of electromagnetic communication, where the distance between transmitter and receiver plays a pivotal role in determining signal intensity. Understanding this relationship is not just an academic endeavour; it’s essential for designing and optimising communication systems in our increasingly connected world. This guide serves as your beacon, shining a light on each concept with clarity and precision, making the journey from concept to understanding both manageable and enlightening.

Inside Your Guide

Foundational Knowledge: Begin with the basics of electromagnetic communication, including an overview of electromagnetic waves and how they are used to transmit information across distances.

Core Principles Unveiled: Delve into the heart of the matter with a clear explanation of how and why signal intensity changes with distance. Learn about the inverse-square law, attenuation, and other factors that influence signal strength.

Practical Applications: Discover the real-world implications of the distance-intensity relationship in telecommunications, broadcasting, and other fields. Understand how this knowledge enhances the efficiency and reliability of communication systems.

Interactive Learning: Engage with exercises and real-life scenarios designed to reinforce your understanding and apply what you’ve learned. These activities solidify your grasp of the concepts and make learning an active and enjoyable process.

Why Choose This Guide?

Clarity and Simplicity: We’ve distilled complex scientific concepts into straightforward explanations. Short sentences and a focus on clarity ensure the material is accessible and enjoyable for all readers.

Active Engagement: This guide emphasizes direct interaction with the content through practical examples and challenges, fostering a deeper understanding and a more enjoyable learning experience.

Comprehensive Coverage: From fundamental physics to advanced communication technologies, this guide thoroughly examines distance and intensity in electromagnetic communication, preparing you for further study or practical application.

Empower Your Understanding: Armed with the insights from this guide, you’ll approach the study of electromagnetic communication with newfound confidence. Understanding the distance-intensity relationship is crucial for anyone involved in or interested in communication technology.

Begin Your Journey of Discovery

Physics in Action: How Distance Impacts Energy” is more than just a study aid; it’s a key to unlocking the complexities of how we communicate across distances. Whether pursuing academic excellence, advancing your career in communication technology, or exploring the physics of communication, this guide offers a clear, engaging pathway to mastering an essential aspect of electromagnetic communication.

Embark on this enlightening journey today. With “Distance vs. Intensity in Electromagnetic Communication,” you’re not just learning about physics; you’re unlocking the secrets of how information travels in our modern world. Start your adventure now and explore the dynamic interplay between distance and signal intensity in electromagnetic communication.

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Additional information


Energy Spreading Out
As a wave travels, the total
energy that it carries does
not change.
However, some waves will
spread out as they travel.
This means that the energy
that they carry is also spread
out over a larger area.

Receiving a Wave
The further away you are
from the source of the waves,
the more the wave spreads
out before it arrives.
You can increase the amount
of energy you receive by
increasing the size of the

Energy of a Wave
In a 3D wave, the energy
spreads out in a sphere.
At a distance of d from the
source, the energy is spread
over a sphere of radius d.

Measuring Intensity
The energy carried by a wave
to a given area per second is
the wave’s intensity (I).
This is called the inverse
square law.

The Inverse Square Law
A consequence of the inverse
square law is that a light
twice as far away will appear
four times as dim.
This is true for all 3D waves,
 Light waves
 Radio waves
 Sound waves

The intensity of the light from a light bulb is 1.8 W m-2 at a
distance of 25 cm. What is the intensity at a distance of 1 m?
The distance increases by a factor of 1/0.25 = 4.
Therefore, the intensity decreases by a factor of 1/16.

Question 1
As the distance from the source of a 3D wave increases, how
does its intensity change?
(A) It increases linearly with distance.
(B) It increases at a rate proportional to the square of the
(C) It decreases linearly with distance.
(D) It decreases at a rate proportional to the square of the
distance. ←
The energy of the wave is spread out over a sphere, which
has area proportional to the square of the distance.

Question 2
Which of the following is an example of a 3D wave?
(A) Starlight from the night sky ←
(B) A compression wave in a spring
(C) Ripples in a pool of water
(D) A signal in an electrical circuit
Light (including starlight) is an electromagnetic wave that
spreads out in all three dimensions: forwards-backwards,
left-right, and up-down.

Question 3
At a certain distance from a source of 3D waves, d, the
intensity of the waves is given by I. Find the intensity at a
distance of:

Question 4
The total power output of a source of waves at a given
distance from the source, d, can be found by multiplying the
intensity at d by the area of a sphere with radius d.
(a) A light bulb has an
intensity of 6 W m–2 at
2 m from the bulb. Find
its total power output.
(b) What is its intensity and
total power output at a
distance of 4 m?

Question 5
Two stars in the sky, Dra and 107 Psc, are known to have
equal total power (luminosity). If Dra is 18.8 light-years
from the Earth, and looks 1.69 times brighter than 107 Psc,
how far away is 107 Psc?