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Laser question with energy.

A laser emits a strong light pulse with a power equal to 10^14 W. The pulse lasts 2 ns.
a) How much energy was delivered?
I used E = Pt and got E=2.0x10^5 J

b) If the laser energy follows from the discharge of a bank of capacitors (with a capacitance of 0.26F) and only 0.3% of the energy has been converted into light, how strong was the initial voltage difference in the capacitor?

So 0.3%= the pulse energy, 100% = energy of the capacitor, does E=2.0x10^5 J + 199400 J = 399400 J? Which equation do I use next to find the initial voltage difference?
Original post by Airess3
A laser emits a strong light pulse with a power equal to 10^14 W. The pulse lasts 2 ns.
a) How much energy was delivered?
I used E = Pt and got E=2.0x10^5 J

b) If the laser energy follows from the discharge of a bank of capacitors (with a capacitance of 0.26F) and only 0.3% of the energy has been converted into light, how strong was the initial voltage difference in the capacitor?

So 0.3%= the pulse energy, 100% = energy of the capacitor, does E=2.0x10^5 J + 199400 J = 399400 J? Which equation do I use next to find the initial voltage difference?


EDITED: my bad, your original pulse energy calc is correct @ 2x105J. Apologies.

If 0.3% = pulse energy

how much is 100%?

Use the 100% calculated energy value together with the stated capacitance (0.26F) substituted into the capacitor stored energy equation.

Pulse energy:

Spoiler



Capacitor stored energy equation:

Spoiler



Total energy stored in the capacitor:

Spoiler



Plate voltage:


Spoiler

(edited 9 years ago)

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