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JEE Mains | PYQ

A point light source emits E.M. waves in free space. A detector, placed at a distance of \( L \, \text{m} \), measure the intensity as \( I_0 \). The detector is now shifted to another location on the same spherical surface ensuring the angle between original location and new location as \( 45^\circ \). The measured intensity at new location will be ______.

The electric field of a plane electromagnetic wave, travelling in an unknown non-magnetic medium is given by, \( E_y = 20 \sin(3 \times 10^6 x - 4.5 \times 10^{14} t) \, \text{V} / \text{m} \) (where \( x \), \( t \) and other values have S.I units). The dielectric constant of the medium is _______. (speed of light in free space is \( 3 \times 10^8 \, \text{m} / \text{s} \))

The electric field in a plane electromagnetic wave is given by:

$E_y = 69 \sin \left[ 0.6 \times 10^3 x - 1.8 \times 10^{11} t \right] \text{V/m}.$

The expression for magnetic field associated with this electromagnetic wave is ________.

An electromagnetic wave travels in free space along the \( x \)-direction. At a particular point in space and time, \( \vec{B} = 2 \times 10^{-7} \, \hat{j} \, \text{T} \) is associated with this wave. The value of corresponding electric field \( \vec{E} \) at this point is ______ \( \text{V/m} \).

Given below are two statements one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The electromagnetic wave exerts pressure on the surface on which they are allowed to fall.
Reason (R): There is no mass associated with the electromagnetic waves.
In the light of the above statements, choose the correct answer from the options given below: