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MODEL PAPER 9 — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsMODEL PAPER 94 Marks
Question
In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels.
(i) The electromagnetic waves propagated perpendicular to both $\vec{E}$ and $\vec{B}$. The electromagnetic waves travel in the direction of
(a) $\vec{E} \cdot \vec{B}$
(b) $\vec{B} \cdot \vec{E}$
(c) $\vec{E} \times \vec{B}$
(d) $\vec{B} \times \vec{E}$

(ii) Fundamental particle in an electromagnetic wave is
(a) photon (b) phonon (c) electron (d) proton

(iii) Electromagnetic waves are transverse in nature is evident by
(a) diffraction (b) interference (c) polarisation (d) reflection

OR

The electric and magnetic fields of an electromagnetic waves are
(a) in opposite phase and parallel to each other
(b) in phase and parallel to each other.
(c) in phase and perpendicular to each other
(d) in opposite phase and perpendicular to each other

(iv) d) in opposite phase and perpendicular to each other
(a) frequency (b) wavelength (c) velocity (d) all these depend on each other
✓

Answer

In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels. (i) (c) $\vec{E} \times \vec{B}$
Explanation: Electromagnetic waves propagate in the direction of $\vec{E} \times \vec{B}$.

(ii) (a) photon
Explanation: Photon is the fundamental particle in an electromagnetic wave

(iii) (c) polarisation
Explanation: Polarisation establishes the wave nature of electromagnetic waves.

OR

(c) in phase and perpendicular to each other
Explanation: The electric and magnetic fields of an electromagnetic wave are in phase and perpendicular to each other.

(iv) (c) in phase and perpendicular to each other
Explanation: The electric and magnetic fields of an electromagnetic wave are in phase and perpendicular to each other.

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