JEE Main 201912 AprilMorning Shift
- Exam
- JEE Main
- Year
- 2019
- Date
- 12 April
- Shift
- Morning Shift
- Subject
- Physics
- Chapter
- Electromagnetic Waves
JEE Main 2019 · 12 April · Morning Shift · Physics · Electromagnetic Waves
An electromagnetic wave is represented by the electric filed → E =...
An electromagnetic wave is represented by the electric filed \overset{\to}{E} = {E}_{0}\overset{^}{n}\sin \left[\omegat + \left(6y - 8z\right)\right] . Taking unit vectors in and directions to be \overset{^}{i}, \overset{^}{j}, \overset{^}{k}, the directions of propogations \overset{^}{s}, is:
Options
- A\overset{^}{s} = \dfrac{3\overset{^}{i} - 4\overset{^}{j}}{5}
- B\overset{^}{s} = \left(\dfrac{- 3\overset{^}{i} + 4\overset{^}{j}}{5}\right)
- C\overset{^}{s} = \dfrac{4\overset{^}{i} - 3\overset{^}{k}}{5}
- D\overset{^}{s} = \dfrac{- 4\overset{^}{i} - 3\overset{^}{k}}{5}
Correct answer
B. \overset{^}{s} = \left(\dfrac{- 3\overset{^}{i} + 4\overset{^}{j}}{5}\right)
Step-by-step solution
The standard equation of electromagnetic wave \overset{\to}{E} = {E}_{0}\overset{^}{n}\sin \left[\omegat - k\overset{^}{x}\right]
here \overset{^}{x}represents the direction of propagation wave.
On comparing the given equation with the standard equation, the direction of propagation is along line . Thus, unit vector along the direction of propagation is,\overset{^}{s} = \dfrac{- 6\overset{^}{j} + 8\overset{^}{k}}{10} = - \dfrac{3}{5}\overset{^}{j} + \dfrac{4}{5}\overset{^}{k}