Physics MCQs for NEET — Practice Questions with Answers

The SI unit of displacement current is the Ampere (A). Displacement current is a quantity appearing in Maxwell's equations and is defined in terms of the rate of change of the electric field. Since it has the same units as regular current, the unit is Ampere.

Electromagnetic waves transport energy, momentum, and information, but they do not transport charge. Charge is a property of particles, not waves. Therefore, the correct option is 'Charge'.

When a plane electromagnetic wave is incident on a material surface, it transfers both energy and momentum. Therefore, both p (momentum) and E (energy) are not zero.

Maxwell's modified form of Ampere's circuital law includes the displacement current term and is given by: $$ \oint \\vec B . d \\vec l = \\\mu_0 i + \\\mu_0 \\\varepsilon_0 { \\frac{d \\\\varphi_E}{dt} } $$ This accounts for the changing electric field in addition to the current.

X-rays have wavelengths in the range of $10^{-8}$ to $10^{-12}$ meters. Therefore, the order of magnitude for the wavelength of X-rays is typically around $10^{-10}$ meters.

The wave number $k$ and angular frequency $ ext{ω}$ relationship is given by $k = rac{2 ext{π} n}{ ext{λ}}$ and $ ext{ω} = rac{2 ext{π} c}{ ext{λ}}$, where $n$ is the refractive index, $ ext{λ}$ is the wavelength, and $c$ is the speed of light. Given the equation $E_z = 100 ext{cos} (6 imes 10^8 t + 4x)$, we can identify $ ext{ω} = 6 imes 10^8$ rad/s and $k = 4 ext{m}^{-1}$. Using the relation $c = rac{ ext{ω}}{k}$, we find $c = rac{6 imes 10^8 ext{rad/s}}{4 ext{m}^{-1}} = 1.5 imes 10^8 ext{m/s}$. The refractive index $n$ can be calculated using $n = rac{c_{ ext{vacuum}}}{c} = rac{3 imes 10^8 ext{m/s}}{1.5 imes 10^8 ext{m/s}} = 2$.