Capacitors

JEE Main level, numerical answer, medium

136 of 180

Question 136 of 180

Suppose that intensity of a laser is (315π)Wm−2.\left(\dfrac{315}{\pi }\right)W{m}^{-2}. The rms electric field, in units of Vm−1V{m}^{-1} associated with this source is close to the nearest integer is −(ϵ0=8.86×10−12C2Nm−2;c=3×108ms−1)-\left({\epsilon }_{0}=8.86\times {10}^{-12}{C}^{2}N{m}^{-2};c=3\times {10}^{8}m{s}^{-1}\right)

Show answer and solution

Answer: 275

12C∈0Ems2=315π\dfrac{1}{2}C{\in }_{0}{E}_{ms}^{2}=\dfrac{315}{\pi }
Erms=315×2π×3×108×8.86×10−12{E}_{rms}=\sqrt{\dfrac{315\times 2}{\pi \times 3\times {10}^{8}\times 8.86\times {10}^{-12}}}
=63083.4612×10−4=\sqrt{\dfrac{630}{83.4612\times {10}^{-4}}}
=7.5484×104=\sqrt{7.5484\times {10}^{4}}
=2.75×102=2.75×102=275=2.75\times {10}^{2}=2.75\times {10}^{2}=275

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.
See it move: Capacitors, dielectrics and RC circuits simulationDrag the sliders and watch the numbers in this question change.

More Physics practice

JEE Main Physics practice question on Capacitors (Force and Energy stored in capacitor), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.