# Number of photons/volume surrounding radio transmitter

• Mika3
In summary, the conversation is about finding a method for calculating the number of photons present within a given volume surrounding a radio transmitter, at a given power and frequency. The equations involved include E=hv, as well as others relating to power and wavelength. The challenge is determining the number of photons within a spherical volume with the transmitter at the center. The solution involves calculating the number of photons produced at a constant rate within a given radius, assuming they move away from the source at the speed of light.
Mika3

## Homework Statement

Seeking a method of calculating the number of photons instantaneously present within a given volume surrounding a radio transmitter at given power and frequency.

## Homework Equations

$$E=hv$$, and other equations involving power and wavelength.

## The Attempt at a Solution

I have no problem calculating the photon energy, and number of photons/second at a given frequency and transmitter power. But how to calculate the number of photons within a given spherical volume, with the transmitter in the center (assuming spherically-symmetrical pattern)?

For example: number of photons within the near-field at x watts and y frequency (I know things can get complicated in the near-field). This is for my own curiosity and is not a textbook question (at least not one that I am aware of). I do not know where to start.

If, as you say, you have no problem with finding the number of photons of a given wavelength produced in, say, a second, then just determine how many of those photons will still be within the given radius of the source. Assume that the photons are produced at a constant rate during that second and that they move away from the source with speed, of course, c.

Thank you HallsofIvy. I was getting confused about the near-field, but real emitted photons are the only thing we have to work with you are right.

## What is the definition of "number of photons/volume surrounding radio transmitter"?

The number of photons/volume surrounding a radio transmitter refers to the density of photons (particles of light) in the immediate vicinity of the transmitter. This measurement is important in understanding the strength and reach of a radio signal.

## How is the number of photons/volume surrounding a radio transmitter measured?

The number of photons/volume is typically measured using a device called a photometer, which can detect and quantify the number of photons in a given volume of space. This measurement can also be estimated using mathematical equations based on the power output and frequency of the radio transmitter.

## What factors can affect the number of photons/volume surrounding a radio transmitter?

The number of photons/volume can be affected by various factors such as the power output of the transmitter, the frequency of the radio waves, and the distance from the transmitter. Other environmental factors such as obstacles and atmospheric conditions can also impact the number of photons/volume.

## Why is the number of photons/volume important in radio communication?

The number of photons/volume is important in radio communication because it directly affects the strength and reach of the radio signal. The higher the number of photons/volume, the stronger the signal and the further it can travel. This is crucial in ensuring clear and reliable communication between the transmitter and receiver.

## How does the number of photons/volume change with distance from the radio transmitter?

The number of photons/volume decreases as you move further away from the radio transmitter. This is because the photons spread out and become less concentrated, resulting in a weaker signal. The exact rate of decrease depends on various factors such as the power and frequency of the transmitter, as well as the presence of any obstacles or interference.

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