Your university radio station has a \(5.0-\mathrm{kW}\) radio transmitter that broadcasts uniformly in all directions; listeners within \(15 \mathrm{km}\) have reliable reception. You want to increase the power to double that range. What should be the new power?

Short Answer

Expert verified
To double the range of reception, the new power should be four times the initial power, \(4 \times 5.0 \mathrm{kW} = 20.0 \mathrm{kW}\.

Step by step solution

01

Understanding the Inverse Square Law

The Inverse Square Law can be expressed as \(I = P/4\pi r^2\), where \(I\) is the intensity, \(P\) is the power, and \(r\) is the distance from the source of the signal. The task is to find a new power \(P'\) that would double the range of reception from \(r\) to \(2r\).
02

Applying the Inverse Square Law

First, relate the known initial power \(P\) to the initial range \(r\) via the equation \(P = I \times 4\pi r^2\). Then, consider the increased range of \(2r\) and the unknown new power \(P'\). It is then possible to write down the relationship \(P' = I \times 4\pi (2r)^2\). With the goal of finding \(P'\), \(I\) can be eliminated from the equations.
03

Solving for New Power

By dividing the second equation by the first, \(P'/P = (2r)^2 / r^2 = 4\). Isolating \(P'\), the new power becomes \(P' = 4P\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Radio Transmitter Power
When we talk about the radio transmitter power, we are referring to the amount of energy per unit time (power) that a transmitter uses to send out a radio signal. This power is usually measured in watts (W). In the context of a university radio station, for instance, this power not only defines how strong the signal is at the source, but also has direct implications for how far the signal can travel. As a station increases its power output, say from a 5.0-kW transmitter to a higher value, this signal can potentially reach a wider audience as the enhanced energy allows it to travel further before dissipating.

It's essential for students to understand that while increasing power might extend the reach, there are also practical and regulatory considerations to take into account, such as possible interference with other signals and legal power limits set by telecommunications authorities.
Intensity
The concept of intensity in physics is closely associated with how strong or concentrated a signal or a force is at a certain distance from its source. Specifically for radio signals, it can be defined as the power per unit area. Following the formula expressed in the Inverse Square Law, \(I = \frac{P}{4\pi r^2}\), the intensity decreases as the square of the distance from the radio transmitter increases. This means that if a listener moves twice as far away from the transmitter, the intensity of the signal they receive is not just halved but actually reduced by a factor of four.

Understanding intensity helps in designing and troubleshooting communication systems, such as determining the range of reliable reception based on a given transmitter power, and it's an essential concept in not just radio broadcasting but in various fields like acoustics, optics, and even astronomy.
Range of Reception
The range of reception is the maximum distance at which a radio signal can be received clearly and with sufficient strength by a receiver. Put simply, it is how far your radio waves travel while still being strong enough to be picked up and decoded by a listener's radio. This range depends on several factors, including transmitter power, frequency of transmission, environmental conditions, and any obstructions in the path of the signal like buildings or foliage. In the problem given, the reliable range is 15 km with a 5.0-kW transmitter.

Increasing the range of reception is often a goal for broadcasters seeking a larger audience. The Inverse Square Law is pivotal to understanding how significantly transmitter power must be increased to achieve a desired range increase. For students studying telecommunications or physics, grasping the real-world implications of this concept is invaluable for practical applications.
Physics Problem Solving
Effective physics problem solving often involves a systematic approach to connect the known variables to the unknowns using key physical laws. When faced with a problem like determining the new power needed to double the range of a radio transmitter, it's crucial to begin with a thorough understanding of the underlying principle, which in this case is the Inverse Square Law. From there, the problem becomes a matter of applying this law to relate initial conditions to the desired outcome and manipulating the equations to solve for the unknown variable.

The step by step solution in the exercise demonstrates a logical and methodical process for deriving the new required power. It involves setting up the initial equation using the known values, identifying the goal (doubling the range of reception), and using algebraic manipulation to isolate and solve for the new power. For students, learning this approach is as important as understanding the concepts involved, since a solid problem-solving strategy is not only applicable in physics but almost any analytical or scientific challenge they might encounter.

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