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Physics lasers question help

Need help with (a)(ii)

I use the equation e=pt
I find 1/t

which is 15*10^6/4.5*10-19
=3.33*10^25

But I am a couple of powers of in the mark scheme it says 3.33*10^16
What am I doing wrong?
Reply 1
phys q.png
Reply 2
Original post by aceplayyt
Need help with (a)(ii)

I use the equation e=pt
I find 1/t

which is 15*10^6/4.5*10-19
=3.33*10^25

But I am a couple of powers of in the mark scheme it says 3.33*10^16
What am I doing wrong?


Where did you get 15 * 10^6 from? I believe it is supposed to be 15 * 10^-3, as it is mW (milliwatts) not MW (megawatts). This should give you the correct answer.
Reply 3
Power = n * h * f, therefore n, the number of photons = P/hf, where hf is just the energy of the photons
Reply 4
Original post by cakeboi
Where did you get 15 * 10^6 from? I believe it is supposed to be 15 * 10^-3, as it is mW (milliwatts) not MW (megawatts). This should give you the correct answer.


OOOOHHH yep did Mega watts instead thanks

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