To find out the number of photons emitted per second by the laser, we can use the relationship between the energy of a single photon, the total energy emitted per second (power), and the number of photons emitted per second. The energy $E$ of a single photon is given by Planck's equation:

$$ E = hf $$

where:

• $ h $ is Planck's constant ($ 6.63 \times 10^{-34} \mathrm{Js} $), and
• $ f $ is the frequency of the light ($ 6 \times 10^{14} \mathrm{Hz} $).

Let's first calculate the energy of one photon:

$$ E = (6.63 \times 10^{-34} \mathrm{Js}) \times (6 \times 10^{14} \mathrm{Hz}) $$

$$ E = 3.978 \times 10^{-19} \mathrm{J} $$

The power ($ P $) emitted by the laser is the total energy emitted per second,

$$ P = E_{\text{total per second}} = 2 \times 10^{-3} \mathrm{W} = 2 \times 10^{-3} \mathrm{J/s} $$

The number of photons ($ N $) emitted per second can be found by dividing the total energy emitted per second by the energy of one photon:

$$ N = \frac{P}{E} $$

Substitute the values we have:

$$ N = \frac{2 \times 10^{-3} \mathrm{J/s}}{3.978 \times 10^{-19} \mathrm{J}} $$

$$ N = \frac{2 \times 10^{-3}}{3.978 \times 10^{-19}} $$

$$ N = 5.03 \times 10^{15} \text{ photons per second} $$

The number of photons emitted per second is approximately $5 \times 10^{15}$. Therefore, the correct answer, rounded to one significant figure, is:

Option A: $5 \times 10^{15}$