A laser produces a beam of light of frequency 5×1014‌Hz with an output power of 33 mW . The average number of photons emitted by the laser per second is (. Planck's constant =6.6×10−34Js)
Step 1: Understanding Power Power is how much energy is used or given out each second. So: Power =‌
‌ Energy ‌
‌ Time ‌
Step 2: Energy of One Photon The energy in one photon of light is found using: E=hf where h is Planck's constant and f is the frequency. Step 3: Total Energy from Many Photons If N photons come out in time t, the total energy is N×hf. Step 4: Linking Power and Number of Photons So, Power =‌
‌ Total Energy ‌
‌ Time ‌
=‌
N×hf
t
Step 5: Average Number of Photons per Second The number of photons per second is n=‌
N
t
=‌
P
hf
Plug in the numbers: n=‌
33×10−3
6.6×10−34×5×1014
Step 6: Final Calculation This works out to: n=10×1016 So, the laser gives off 10×1016 photons every second.