Electromagnetic Waves Chapter-Wise Test 16

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What does the Ampere-Maxwell law relate in Maxwell's equations?

The Ampere-Maxwell law relates the magnetic field to both the conduction current and the displacement current, given by \( \oint \mathbf{B} \cdot \mathrm{d} \mathbf{l} = \mu_0 i_c + \mu_0 \varepsilon_0 \frac{d \Phi_E}{dt} \).

Magnetic field to conduction and displacement currents
Electric field to magnetic flux
Magnetic field to charge
Electric field to conduction current only
1

Why does the depletion of the ozone layer pose a significant health risk?

The ozone layer absorbs most of the sun’s harmful UV radiation; its depletion allows more UV rays to reach the Earth, increasing risks of skin cancer and other health issues.

It increases infrared radiation
It reduces greenhouse gases
It increases UV radiation exposure
It enhances radio wave interference
3

An electromagnetic wave in vacuum has a wavelength of \( 15 \, \text{m} \). What is its frequency? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( v \lambda = c \), we have \( v = \frac{c}{\lambda} = \frac{3 \times 10^8}{15} = 2 \times 10^7 \, \text{Hz} \).

\( 1.5 \times 10^7 \, \text{Hz} \)
\( 1.75 \times 10^7 \, \text{Hz} \)
\( 2 \times 10^7 \, \text{Hz} \)
\( 2.5 \times 10^7 \, \text{Hz} \)
3

What is one technological importance of electromagnetic waves mentioned in the document?

The document highlights that electromagnetic waves carry energy, enabling applications like radio and TV signals from broadcasting stations.

They require a medium to propagate
They have variable speeds
They are all visible
They carry energy for communication
4

Why are gamma rays used in medical applications to treat cancer?

Gamma rays have very high energy and penetrating power due to their short wavelengths, allowing them to target and destroy cancer cells effectively.

They heat tissues
They emit visible light
They destroy cancer cells
They enhance cell growth
3

In electromagnetic theory, what fundamental principle allows electromagnetic waves to sustain their propagation in vacuum without energy loss?

The principle of mutual induction, where a changing electric field induces a magnetic field and vice versa (via Faraday’s law and Ampere-Maxwell law), ensures self-sustaining propagation in vacuum without energy loss.

Mutual induction of fields
Presence of a medium
Static field interactions
Energy dissipation
1

What is a common method to detect gamma rays as per the document?

The document lists photographic film, Geiger tubes, and ionization chambers as detectors for gamma rays. Geiger tubes are a common choice.

Photocells
Thermopiles
Geiger tubes
Receiver's aerials
3

What is the primary source of infrared waves mentioned in the document?

The document states that infrared waves are produced by hot bodies and molecules, such as those in thermal environments.

The sun
Nuclear reactions
Hot bodies and molecules
Special lamps
3

What role does the displacement current play in a region where there is no conduction current?

The document explains that in regions with no conduction current but a time-varying electric field, displacement current acts as a source of magnetic field, enabling electromagnetic wave propagation.

It acts as a source of magnetic field
It cancels electric fields
It produces conduction current
It eliminates magnetic fields
1

Why does the absence of magnetic monopoles imply a specific property about magnetic field lines?

The absence of magnetic monopoles, as stated by Gauss’s law for magnetism, implies that magnetic field lines are always closed loops, with no isolated sources or sinks.

Magnetic field lines form closed loops
Magnetic field lines are always straight
Magnetic field lines can diverge indefinitely
Magnetic field lines originate from currents
1

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