- #1

Yroyathon

- 42

- 0

## Homework Statement

A scientist wishes to study the behavior of individual photons. To do that, she must decrease the intensity of her i_1 mm2 laser beam -- the laser emits radiation with wavelength w_1 nm -- to a level at which there is no more than one photon in her apparatus at any given time. The path length of the light beam from source to detector is L_1 m. What should be the intensity?

## Homework Equations

for intensity I've used I=P/A, power over area.

for Power of the laser in terms of the photons, I used P = N * E, where N is the number of photons and E is the energy of a photon. for calculating the energy of a photon I used E = h*c/w_1, where h is Planck's constant, c is the speed of light, and w_1 is the wavelength. so in this problem, P = N*6.6*10^(-34)*(3*10^8))/(w_1*10^(-9)).

## The Attempt at a Solution

Hmm. I guess I just realized I wasn't sure what to use for A in the equation for intensity. I think in my first guess I just set A=1, without really thinking.

In my guess I realized I didn't use the distance L_1, which I feel is bad. I wasn't really sure how to incorporate it into the problem.

So I'm considering the quantity of L_1/c, which might be how long it takes a photon to reach the detector? but I'm not certain of this.

I'm not getting this right because using my conceptual understanding of the scenario and the equations i have at hand, I don't have a complete cohesive picture.

Any tips would be appreciated. Thanks.

,Yroyathon