Electromagnetic Waves Chapter-Wise Test 23

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the primary source of gamma rays mentioned in the document?

The document states that gamma rays are produced in nuclear reactions and emitted by radioactive nuclei.

Hot bodies
Special lamps
Nuclear reactions
Electron acceleration
3

What is the expression for displacement current as given in the document?

The document provides the expression for displacement current as \( i_d = \varepsilon_0 \frac{d \Phi_E}{dt} \), where \( \Phi_E \) is the electric flux.

\( i_d = \varepsilon_0 \frac{d \Phi_E}{dt} \)
\( i_d = \mu_0 \frac{d \Phi_B}{dt} \)
\( i_d = \frac{dQ}{dt} \varepsilon_0 \)
\( i_d = \frac{d \Phi_E}{dt} / \varepsilon_0 \)
1

Why are radio waves used in communication systems like cellular phones?

Radio waves can travel long distances and penetrate obstacles like buildings due to their long wavelengths, making them ideal for communication systems.

They have short wavelengths
They are absorbed by obstacles
They travel slower than light
They travel long distances
4

What is the approximate wavelength range of X-rays?

As per the document, X-rays have wavelengths from about \( 10^{-8} \, \text{m} \) (10 nm) to \( 10^{-13} \, \text{m} \) (\( 10^{-4} \, \text{nm} \)).

\( 1 \, \text{mm} \) to \( 700 \, \text{nm} \)
\( 400 \, \text{nm} \) to \( 1 \, \text{nm} \)
\( 10 \, \text{nm} \) to \( 10^{-4} \, \text{nm} \)
\( > 0.1 \, \text{m} \)
3

What property of electromagnetic waves allows them to exhibit phenomena like interference?

Electromagnetic waves have wave-like properties, such as sinusoidal oscillations and coherence, which allow superposition and interference to occur under suitable conditions.

Wave-like properties
Particle nature
Static field behavior
Medium dependence
1

An electromagnetic wave in vacuum has an electric field amplitude of \( 60 \, \text{V/m} \). What is the magnetic field amplitude? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( B_0 = \frac{E_0}{c} \), we have \( B_0 = \frac{60}{3 \times 10^8} = 2 \times 10^{-7} \, \text{T} \).

\( 1 \times 10^{-7} \, \text{T} \)
\( 1.5 \times 10^{-7} \, \text{T} \)
\( 1.8 \times 10^{-7} \, \text{T} \)
\( 2 \times 10^{-7} \, \text{T} \)
4

Which type of electromagnetic waves are produced by the vibration of atoms and molecules?

The document states that infrared waves are produced by the vibration of atoms and molecules.

Radio waves
Infrared waves
Microwaves
Ultraviolet waves
2

What is the frequency range of the AM radio band?

The document states that the AM (amplitude modulated) band ranges from \( 530 \, \text{kHz} \) to \( 1710 \, \text{kHz} \).

\( 88 \, \text{MHz} \) to \( 108 \, \text{MHz} \)
\( 54 \, \text{MHz} \) to \( 890 \, \text{MHz} \)
\( 530 \, \text{kHz} \) to \( 1710 \, \text{kHz} \)
\( 500 \, \text{kHz} \) to \( 1000 \, \text{MHz} \)
3

What physical quantity is the same for all electromagnetic waves in vacuum?

All electromagnetic waves in vacuum travel at the same speed, \( c = 3 \times 10^8 \, \text{m/s} \), regardless of their frequency or wavelength.

Frequency
Wavelength
Speed
Energy
3

What type of charges cannot produce electromagnetic waves?

The document states that neither stationary charges nor charges in uniform motion (steady currents) can produce electromagnetic waves; only accelerated charges can.

Stationary charges
Accelerated charges
Oscillating charges
Charges in circular motion
1

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