- #1

heycoa

- 75

- 0

## Homework Statement

Suppose a laser produces a pulse of light with duration 1 ns, a diameter of 1 cm, and a total energy of 1 mJ. In free space, the pulse length is this 30 cm, the energy density is 42 J/m

^{3}, and the irradiance is 1.3*10

^{10}W/m

^{2}. Calculate the length, energy density, and irradiance if the pulse with the same duration, diameter, and total energy is instead in a medium with refractive index n = 1.5. Compare the electric fields for the two cases.

## Homework Equations

Irradiance = c*ε

_{0}/2 * E

_{0}

^{2}

Energy Density = .5*ε

_{0}*E

^{2}+ .5*B

^{2}/μ

_{0}

Frequency=c/n

Wave number k=n*ω/c

## The Attempt at a Solution

I do not know how "energy density" and "total energy" differ and/or are related. I also am having a difficult time distingushing the separation between free space and a medium with a refractive index. But perhaps my biggest struggle is how to put to use the length, pulse duration, and diameter. I guess this is a geometrical problem however, I just cannot understand how to utilize the measurements.

Please help me understand this. All your help and time is greatly appreciated!

Thank you