PYQ Vault
EbooksTutor

Electric and magnetic forces on a charge moving in an EM wave

This type of question, asked 4 times: 2021 Paper 19, 2021 Paper 23, 27 Jul 2022, 2 Apr 2026 S1. All 4 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    2021 Paper 19

    6
    A light beam is described by E=800sin⁡ω(t−xC)E = 800\sin\omega\left( t -\frac{x}{C} \right) .An electron is allowed to move normal to the propagation of light beam with a speed of 3×1073 \times10^{7} ms−1ms^{- 1}. What is the maximum magnetic force exerted on the electron?

    Tap an option to check your answer.

  2. Question 2

    2021 Paper 23

    12
    The magnetic field vector of an electromagnetic wave is given by B=Boi^+j^2cos⁡(kz−ωt)B=B_{o}\frac{\widehat{i}+\widehat{j}}{\sqrt{2}}\cos(kz-\omega t); where i^,j^\widehat{i},\widehat{j} represents unit vector along xx and yy-axis respectively. At t=0 st = 0\text{ }s, two electric charges q1q_{1} of 4π4\pi coulomb and q2q_{2} of 2π2\pi coulomb located at (0,0,πk)\left( 0,0,\frac{\pi}{k} \right) and (0,0,3πk)\left( 0,0,\frac{3\pi}{k} \right), respectively, have the same velocity of 0.5ci^0.5c\widehat{i}, (where cc is the velocity of light). The ratio of the force acting on charge q1q_{1} to q2q_{2} is:

    Tap an option to check your answer.

  3. Question 3

    27 Jul 2022

    15
    A beam of light travelling along XX-axis is described by the electric field Ey=900sin⁡ω(t−x/c)E_{y}= 900\sin\omega(t - x/c). The ratio of electric force to magnetic force on a charge qq moving along YY-axis with a speed of 3×107 ms−13 \times10^{7}{\text{ }ms}^{- 1} will be: [Given speed of light =3×108 ms−1= 3 \times10^{8}{\text{ }ms}^{- 1} ]

    Tap an option to check your answer.

  4. Question 4

    2 Apr 2026 S1

    18
    An electromagnetic wave travelling in x -direction is described by field equation Ey=300sin⁡ω(t−xc)E_{y}= 300\sin\omega\left( t -\frac{x}{c} \right). If the electron is restricted to move in y -direction only with speed of 1.5×106 m/s1.5 \times10^{6}\text{ }m/s then ratio of maximum electric and magnetic forces acting on the electron is ____\_\_\_\_ .

    Tap an option to check your answer.