1. What is the Photon Count Equation?

The photon count equation calculates the number of photons (n) received at a certain distance from a light source, accounting for the inverse square law of light propagation through space.

2. How Does the Calculator Work?

The calculator uses the photon count equation:

Where:

• \( P \) — Power of the light source (W)
• \( t \) — Time duration (s)
• \( E \) — Energy per photon (J/photon)
• \( r \) — Distance from the source (m)

Explanation: The equation accounts for the spreading of light over distance (inverse square law) and converts the total energy to number of photons.

3. Importance of Photon Calculation

Details: Calculating photon counts at different distances is crucial for applications like optical communications, photovoltaics, spectroscopy, and quantum optics experiments.

4. Using the Calculator

Tips: Enter power in watts, time in seconds, energy per photon in joules, and distance in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why does distance affect photon count?
A: Due to the inverse square law - light spreads out over a larger area as distance increases, reducing the photon density.

Q2: How do I calculate energy per photon?
A: Use E = hc/λ, where h is Planck's constant, c is light speed, and λ is wavelength.

Q3: Does this account for absorption or scattering?
A: No, this is the theoretical maximum in vacuum. Real-world applications need additional attenuation factors.

Q4: What's a typical photon count for visible light?
A: A 1W green light (λ≈500nm) emits about 3×10¹⁸ photons per second at the source.

Q5: Can this be used for single-photon detectors?
A: Yes, it helps estimate detection rates at different distances from weak light sources.