NEET Practice Questions (MCQs) with Answers & Solutions

The given equation $\oint \vec{E} \cdot d\vec{t} = -\frac{d\Phi_B}{dt}$ is Faraday's law of electromagnetic induction. This law states that a changing magnetic field within a closed loop induces an electromotive force (EMF) in the loop. The negative sign indicates the direction of the induced EMF, which opposes the change in magnetic flux, as per Lenz's law.

In an electromagnetic wave, both the electric field (\(\vec{E}\)) and the magnetic field (\(\vec{B}\)) oscillate perpendicular to each other and to the direction of wave propagation. This is a fundamental characteristic of electromagnetic waves.

The average total energy density (u) of an electromagnetic wave is given by the equation: \[ u = \frac{1}{2} \epsilon_0 E_{rms}^2 \] where \( \epsilon_0 \) is the permittivity of free space (\( 8.854 \times 10^{-12} \) F/m) and \( E_{rms} \) is the rms value of the electric field. Given \( E_{rms} = 720 \) N/C: \[ u = \frac{1}{2} \times 8.854 \times 10^{-12} \times (720)^2 \approx 4.58 \times 10^{-6} \text{ J/m}^3 \] Therefore, the correct option is \( 4.58 \times 10^{-6} \text{ J/m}^3 \).

The wavelength range of visible light lies approximately between 4000 \( A^\circ \) (400 nm) and 7000 \( A^\circ \) (700 nm). This range corresponds to the spectrum of light that is visible to the human eye. Therefore, the correct option is \( 4000 \text{ A}^\circ \text{ to } 7000 \text{ A}^\circ \).

The visible light spectrum ranges between ultraviolet (UV) rays and infrared (IR) rays. The wavelength of visible light ranges from approximately 400 nm to 700 nm.

Electromagnetic waves are transverse waves, not longitudinal waves. Longitudinal waves are waves where the particle displacement is parallel to the direction of wave propagation, like sound waves. Electromagnetic waves have oscillating electric and magnetic fields perpendicular to the direction of propagation.

In electromagnetic waves, the electric field (E) and magnetic field (B) vectors are mutually perpendicular to each other and also perpendicular to the direction of wave propagation. They oscillate in phase, meaning that their peaks and troughs occur simultaneously.