Question

A ruby laser delivers a 16.0-ns pulse of 4.20-MW average power. If the photons have a wavelength of 694.3 nm, how many are contained in the pulse

Answer 1

The value is
`n = 2.347 *10^(17) \ photons`

Step-by-step explanation:

From the question we are told that

The amount of power delivered is
`P = 4.20 \ M W = 4.20 *10^(6) \ W`

The time taken is
`t = 16.0ns = 16.0 *10^(-9) \ s`

The wavelength is
`\lambda = 694.3 \ nm = 694.3 *10^(-9) \ m`

Generally the energy delivered is mathematically represented as

`E = P * t = (n * h * c )/(\lambda )`

Where
`h` is the Planck's constant with value
`h = 6.262 *10^(-34) \ J \cdot s`

c is the speed of light with value
`c = 3.0*10^(8) \ m/s`

So

`4.20 *10^(6) * 16*10^(-9)= (n * 6.626 *10^(-34) * 3.0*10^(8) )/(694.3 *10^(-9))`

=>
`n = 2.347 *10^(17) \ photons`