A laser used to weld detached retinas emits light with a wavelength of 652 nm in pulses that are 20 ms in duration. THe average power expended during each pulse is .600 W. (a) How much energy is in each pulse, in joules and electron volts? (b) What is the energy of one photon in joules and electron volts? (c) How many photons are in each pulse?

ok, I know how to get the electronvolts once I get the joules...but I can't figure out the joules! Help please!

watts=energyinjoules/timeinseconds

To calculate the energy in each pulse in joules, you can use the formula:

Energy (Joules) = Power (Watts) x Time (Seconds)

In this case, the average power expended during each pulse is 0.600 W, and the duration of each pulse is 20 ms, which is equivalent to 0.020 seconds.

So, the energy in each pulse in joules can be calculated as:

Energy (Joules) = 0.600 W x 0.020 s = 0.012 Joules

Therefore, each pulse has an energy of 0.012 Joules.

To convert this to electron volts (eV), you can use the conversion factor that 1 eV is equal to 1.6 x 10^(-19) Joules. So, to find the energy in electron volts:

Energy (eV) = Energy (Joules) / (1.6 x 10^(-19))

Substituting the value of the energy in joules:

Energy (eV) = 0.012 J / (1.6 x 10^(-19))

Calculating this expression gives:

Energy (eV) ≈ 7.5 x 10^16 eV

Therefore, each pulse contains approximately 7.5 x 10^16 electron volts of energy.

For the energy of one photon, you can use the relationship between energy, wavelength, and Planck's constant (h):

Energy (Joules) = (h x speed of light) / wavelength

Speed of light in a vacuum is approximately 3 x 10^8 meters per second.

Given the wavelength of the laser light as 652 nm (which is 652 x 10^(-9) meters), you can calculate the energy of one photon:

Energy (Joules) = (6.626 x 10^(-34) J.s x 3 x 10^8 m/s) / (652 x 10^(-9) m)

Calculating this expression will give you the energy of one photon in joules.

To convert this energy to electron volts, you can use the conversion factor mentioned earlier:

Energy (eV) = Energy (Joules) / (1.6 x 10^(-19))

Finally, to find the number of photons in each pulse, you can use the formula:

Number of photons = Energy (Joules) / Energy of one photon (Joules)

Substituting the values:

Number of photons = 0.012 J / (energy of one photon in J)

This will give you the number of photons in each pulse.