2 Marks Questions

Question 12 Marks

Write any four characteristics of electromagnetic wave.

Answer

(i) Electromagnetic waves do not require any material medium for their propagation.
(ii) Electromagnetic waves travel in a straight line.
(iii) The nature of electromagnetic waves is transverse.
(iv) The properties of the medium in which electromagnetic waves travel remain unchanged.

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Question 22 Marks

Write Maxwell's equations.

Answer

Maxwell's equations(i) $\oint \overrightarrow{ E } \cdot \overrightarrow{d A}=\frac{ Q }{\epsilon_0}$ (Gauss's law regarding electricity)(ii) $\oint \overrightarrow{ B } \cdot \overrightarrow{d A}=0 \quad$ (Gauss's law regarding magnetism)(iii) $\oint \overrightarrow{ E } \cdot \overrightarrow{ dl }=\frac{- d \phi_{ B }}{ dt }$ (Faraday's law)(iv) $\oint \overrightarrow{ B } \cdot \overrightarrow{d I }=\mu_0 I _{ C }+\mu_0 \in_0 \frac{d \phi_{ E }}{d t}$ (Ampere-Maxwell's law)

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Question 32 Marks

Write uses of X-rays.

Answer

Uses : (1) In radio astronomy, in amplifying the signals of very weak micro waves signals.
(2) Space communication, used in radio communication for long distances.
(3) Extensively used in medical science and micro surgeries.

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Question 42 Marks

A plane electromagnetic wave is propagating along Y -axis in vacuum. Write about the (i) ratio of magnitudes and (ii) directions of electric and magnetic fields.

Answer

(i) $E / B =c$, where $E =|\overrightarrow{ E }| ; B =|\overrightarrow{ B }|$ and $c=$ speed of light.
(ii) Electric and magnetic field vector $\vec{E}$ and $\vec{B}$ will be respectively along the Z -axis and X -axis. They will be perpendicular to the direction of transmission of wave.

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Question 52 Marks

When does a charge be source of origin of electromagnetic waves? How are the magnetic field and electric field mutually and with the transmission of wave related? Which physical quantity is same for waves of all parts of electromagnetic classification?

Answer

Accelerated electric charge can be a source of origin of electromagnetic waves. Electric and magnetic fields are mutually perpendicular in electromagnetic waves and also perpendicular to the direction of wave propagation. In air or vacuum, speed of all parts of electromagnetic spectrum classification is same which is $c=\frac{1}{\sqrt{\mu_0 \cdot \epsilon_0}}=3 \times 10^8 m / s$.

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Physics 2 Marks Questions

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