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Magnetic field amplitude from the intensity of light

This type of question, asked 3 times: 2021 Paper 13, 29 Jun 2022, 22 Jan 2026 S2. All 3 questions below, oldest first.

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  1. Question 1

    2021 Paper 13

    5
    The intensity of sunlight at a place on earth is 0.92wm−20.92wm^{- 2}. Find the amplitude of magnetic field at that place.

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  2. Question 2

    29 Jun 2022

    22
    The intensity of the light from a bulb incident on a surface is 0.22 W/m20.22\text{ }W/m^{2}. The amplitude of the magnetic field in this light-wave is ____×10−9 T\_\_\_\_ \times10^{- 9}\text{ }T (Given: Permittivity of vacuum ϵ0=8.85×10−12C2 N−1 m−2\epsilon_{0}= 8.85 \times10^{- 12}C^{2}{\text{ }N}^{- 1}{\text{ }m}^{- 2}, speed of light in vacuum c=3×108 ms−1c = 3 \times10^{8}{\text{ }ms}^{- 1} )

  3. Question 3

    22 Jan 2026 S2

    18
    A laser beam has intensity of 4.0×1014 W/m24.0 \times 10^{14}\text{ }W/m^{2}. The amplitude of magnetic field associated with beam is ____\_\_\_\_ T. (Take ϵ0=8.85×10−12C2/Nm2\epsilon_{0} = 8.85 \times 10^{- 12}C^{2}/Nm^{2} and c=3×108 m/sc = 3 \times 10^{8}\text{ }m/s)

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