A laser used to weld detached retinas emits light with a wavelength of 652 nm in pulses that are 20.0ms in duration. The average power during each pulse is 0.6 W. then,

Options

A. the energy of each photon is `3.048xx10^(-19)J`
B. the energy content in each pulse is 12mJ
C. the number of photons in each pulse is nearly `4xx10^(15)`
D. the energy of each photon is nearly 1.9 eV

Explanation

To solve the problem step by step, we will calculate the energy of a single photon, the total energy emitted in a pulse, and finally the number of photons emitted in that pulse.

### Step 1: Calculate the Energy of a Single Photon
The energy of a photon can be calculated using the formula:
\[ E = \frac{hc}{\lambda} \]
where:
- \(E\) is the energy of the photon,
- \(h\) is Planck's constant (\(6.626 \times 10^{-34} \, \text{J s}\)),
- \(c\) is the speed of light (\(3 \times 10^8 \, \text{m/s}\)),
- \(\lambda\) is the wavelength of the light (in meters).

Given:
- \(\lambda = 652 \, \text{nm} = 652 \times 10^{-9} \, \text{m}\)

Substituting the values:
\[ E = \frac{(6.626 \times 10^{-34} \, \text{J s})(3 \times 10^8 \, \text{m/s})}{652 \times 10^{-9} \, \text{m}} \]
Calculating this gives:
\[ E \approx 3.04 \times 10^{-19} \, \text{J} \]

### Step 2: Calculate the Total Energy in a Pulse
The total energy emitted in a pulse can be calculated using the formula:
\[ E_{\text{total}} = P \times t \]
where:
- \(P\) is the average power (in watts),
- \(t\) is the duration of the pulse (in seconds).

Given:
- \(P = 0.6 \, \text{W}\)
- \(t = 20.0 \, \text{ms} = 20.0 \times 10^{-3} \, \text{s}\)

Substituting the values:
\[ E_{\text{total}} = 0.6 \, \text{W} \times 20.0 \times 10^{-3} \, \text{s} = 0.012 \, \text{J} = 12 \, \text{mJ} \]

### Step 3: Calculate the Number of Photons in Each Pulse
The number of photons emitted in a pulse can be calculated using the formula:
\[ N = \frac{E_{\text{total}}}{E} \]
where:
- \(N\) is the number of photons,
- \(E_{\text{total}}\) is the total energy in the pulse,
- \(E\) is the energy of a single photon.

Substituting the values:
\[ N = \frac{0.012 \, \text{J}}{3.04 \times 10^{-19} \, \text{J}} \]
Calculating this gives:
\[ N \approx 3.95 \times 10^{16} \text{ photons} \]

### Final Answers
1. Energy of each photon: \(3.04 \times 10^{-19} \, \text{J}\) or \(1.9 \, \text{eV}\)
2. Total energy in each pulse: \(12 \, \text{mJ}\)
3. Number of photons in each pulse: approximately \(3.95 \times 10^{16}\)