# What is the Photon Flux for a 100 MHz Signal Traveling 4 Light Years Away?

• Ashley1nOnly
In summary, the conversation discusses the problem of capturing photons from a distant source located 4 light years away. The equation E=hf is mentioned, where h represents Plank's constant and f represents frequency. The formula E=(6.6261*10^(-34)) J•s * (100 MHz) is used to calculate the energy of the photons. The number of photons per second is found by dividing the power by the photon energy, and then further divided by 24 to account for the 24 frames per second. The conversation also mentions the need for a large detector or receiver to capture all the photons, and the fact that not all the photons are necessary for the task at hand.
Ashley1nOnly

## Homework Statement

It's in attachment

## Homework Equations

E=hf. Where h= planks constant and f= frequency

## The Attempt at a Solution

I know that the flux of a photon is (# of photons)/(sec m^2)
I don't know the number of photos but I do know the frequency and power.

E=(6.6261*10^(-34)) J•s * (100 MHz)=6.621*10^-32
Also
Wavelength*frequnecy=c
I know that it's traveling 4 light years away.

Wavelength*(100MHz)=4c
Wavelength=4c/(100MHz

What equation am I supposed to use and how do I find the number of photon and how big in diameter would the recover/detector have to be. I don't want the answer just help understanding the problem and what I'm doing wrong. Or am I on the right track

#### Attachments

• image.jpeg
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The image has a wrong orientation.

You know the energy per photon, and the power. Can you get the photons per second, or per image frame?
To capture all photons in a distance of 4 light years, aliens would have to construct a sphere with a radius of 4 light years. They don't need all the photons, of course, but which fraction do they need?

I know the
energy is 6.621*10^-32
power is 100Kw 24 frames per second.

what equation should i use to relate them

I can do the power divided by the photon energy to get the number of photons arriving per second100 KW/ 6.21*10^-32

Ashley1nOnly said:
I can do the power divided by the photon energy to get the number of photons arriving per second
Right.
As every second has 24 frames, how many photons are there per frame?

All those steps all don't need fancy physics.

power divided by / ( the photon energy * 24) to get the number of photons per frame

## What is photon flux?

Photon flux, also known as photon flux density or radiant flux, is a measure of the rate at which photons (particles of light) pass through a given area per unit time. It is commonly measured in units of photons per square meter per second.

## How is photon flux related to modern physics?

Photon flux is a fundamental concept in modern physics, particularly in the study of quantum mechanics and electromagnetism. It is used to understand and describe the behavior of light particles and their interactions with matter.

## What factors affect photon flux?

The intensity of photon flux is affected by several factors, including the energy of the photons, the number of photons emitted per unit time, and the distance between the source of the photons and the area of measurement. Other factors such as the presence of a medium or obstacles in the path of the photons can also influence the photon flux.

## How is photon flux measured?

Photon flux is typically measured using specialized instruments such as photometers or spectrometers. These instruments detect and measure the intensity of light at different wavelengths, allowing for the calculation of photon flux. In modern physics, advanced techniques such as laser spectroscopy and quantum optics are also used to measure photon flux.

## What are some applications of photon flux in modern physics?

Photon flux has numerous applications in modern physics, including in the development of new technologies such as solar cells, lasers, and medical imaging devices. It also plays a crucial role in understanding and studying phenomena such as photosynthesis and the behavior of light in quantum systems.

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