A laser used to weld detached retinas emits light with a wavelength of 652 nm in pulses that are 20.0 ms in duration. The average power during each pulse is 0.600 W. (a) How much energy is in each pulse in joules? In electron volts?

Video transcript

Hi everyone in this practice problem, we're being asked to calculate the energy of pulses of a laser device used for a show during a performance, the laser device emitted pulses each of 25 milliseconds with an average power of 0.7 watt. For each pulse, we're being asked to calculate the energies in jos and E V. If the wavelength of light emitted is 562 nanometer. The options given are a one point oh nine times 10 to the power of negative two joles and 1.75 times 10 to the power of 18 E V B 0.1 oh nine Joles and 1.75 times 10 to the power of 16 E V C 1.75 times 10 to the power of negative three joles and one point oh nine times 10 to the power of 19 E V and D 1.75 times 10 to the power of negative two Joles and one point oh nine times 10 to the power of 17 E V. So for a photon, the average power will be able to calculate that by using the formula of P A V equals to energy or E divided by T energy or E is energy and T is just time P A V is the average power. So in this case, what we are being asked is the energy. So in this case, we can uh rearrange this formula to get the formula for E which will then be equals to P A V multiplied by T. We are given both the P A V and the T. So let's substitute that value into our equation here. So E will then be equals to P A V which is 0. watt. And then the time is given in the problem statement in milliseconds. So we have to convert that by multiplying 25 with 10 to the power of negative three to convert the milliseconds into seconds just like so calculating this, we will then get the energy to then be equals to 1. times 10 to the power of negative two jos. So now we have to convert this jos into E V and we know that one E V will equals to 1.6 oh two times 10 to the power of negative 19 jos. So in order for us to convert the energy into E V, we just have to uh to multiply our equation here with one E V and divided by 1.6 oh two times 10 to the power of negative 19. So we have the energy to be 1.75 times 10 to the power of negative to Jules. So we want to multiply that with one E V and divide that with 1.6 oh two times 10 to the power of negative Joles. And in this, we will then get our energy to then be equals to one point oh nine times 10 to the power of 17 E V. So there we go, We have the energy in jos to be 1.75 times 10 to the power of negative two and the energy in E V which is one point oh nine times to the power of 17 E V. And these answers will correspond to option D in our answer choices. So option D will be the answer to this particular practice problem. So that'll be it for this video. If you guys still have any sort of confusion, please make sure to check out our adolescent videos on our website. But other than that, that'll be it for this one. Thank you.