Question 1

Which of the following statements is true about the production of electromagnetic waves?

Accepted Answer

Correct Option: C. Solution: Accelerated charges radiate electromagnetic waves. This is a fundamental result of Maxwell's theory.

Question 2

In the generalised Ampere-Maxwell law, which of the following represents the total current linked with a surface?

Accepted Answer

Correct Option: C. Solution: The generalised Ampere-Maxwell law states that the total current linked with a surface is the sum of the conduction current and the displacement current, given by $i = i_c + i_d$.

Question 3

In the context of the displacement current, what is the significance of the term $\varepsilon_0 \frac{d\Phi_E}{dt}$?

Accepted Answer

Correct Option: A. Solution: The term $\varepsilon_0 \frac{d\Phi_E}{dt}$ represents the rate of change of electric flux, which contributes to the displacement current in Maxwell's equations.

Question 4

Which of Maxwell's equations in vacuum describes the absence of magnetic monopoles?

Accepted Answer

Correct Option: B. Solution: Gauss's Law for magnetism states that the net magnetic flux through any closed surface is zero, implying the absence of magnetic monopoles.

Question 5

If a plane electromagnetic wave travels in vacuum along the z-direction, what can be said about the directions of its electric and magnetic field vectors?

Accepted Answer

Correct Option: B. Solution: In a plane electromagnetic wave traveling in vacuum, the electric and magnetic field vectors are perpendicular to each other and to the direction of wave propagation, which is characteristic of transverse waves.

Question 6

Which of the following statements correctly describes the production of radio waves?

Accepted Answer

Correct Option: A. Solution: Radio waves are produced by the accelerated motion of electrons in conducting wires, which is a fundamental principle of electromagnetic wave generation.

Question 7

In the context of Maxwell's equations, what is the significance of the Ampere-Maxwell law?

Accepted Answer

Correct Option: C. Solution: The Ampere-Maxwell law generalizes Ampere's law by including the displacement current, which accounts for the time rate of change of electric flux, making the total current the sum of conduction and displacement currents.

Question 8

How does the speed of electromagnetic waves change when they travel through a medium?

Accepted Answer

Correct Option: C. Solution: In a medium, the speed of electromagnetic waves decreases and is given by $v = \frac{1}{\sqrt{\mu \varepsilon}}$, where $\mu$ is the permeability and $\varepsilon$ is the permittivity of the medium.

Question 9

In an electromagnetic wave traveling in vacuum, the ratio of the magnitudes of the electric field $E_0$ to the magnetic field $B_0$ is equal to the speed of light $c$. If the electric field amplitude is $120 \, 	ext{N/C}$, what is the amplitude of the magnetic field?

Accepted Answer

Correct Option: B. Solution: The relation between the electric field $E_0$ and the magnetic field $B_0$ in an electromagnetic wave is given by $E_0/B_0 = c$. Thus, $B_0 = E_0/c = 120 \, 	ext{N/C} / 3 \, 	imes \, 10^8 \, 	ext{m/s} = 4 \, 	imes \, 10^{-7} \, 	ext{T}$.

Question 10

In the context of electromagnetic waves, what is the significance of the displacement current?

Accepted Answer

Correct Option: A. Solution: The displacement current is significant because it allows electromagnetic waves, which are self-sustaining oscillations of electric and magnetic fields, to propagate in space.

Question 11

In a vacuum, the electric field amplitude $E_0$ and magnetic field amplitude $B_0$ of an electromagnetic wave are related by which equation?

Accepted Answer

Correct Option: B. Solution: In a vacuum, the electric field amplitude $E_0$ and magnetic field amplitude $B_0$ are related by $E_0 = cB_0$, where $c$ is the speed of light.

Question 12

During the charging of a capacitor, how does the displacement current compare to the conduction current?

Accepted Answer

Correct Option: C. Solution: During the charging of a capacitor, the displacement current between the plates is equal in magnitude to the conduction current in the wires, ensuring continuity of current.

Question 13

Microwaves are used in radar systems due to their specific properties. Which of the following is a reason for their suitability in radar applications?

Accepted Answer

Correct Option: B. Solution: Microwaves have short wavelengths, which makes them suitable for radar systems as they allow for precise detection and measurement of objects.

Question 14

Which of the following is NOT a common use of infrared waves?

Accepted Answer

Correct Option: C. Solution: Infrared waves are used in remote controls, medical therapy, and satellite detection. X-ray imaging uses X-rays, which are a different part of the electromagnetic spectrum.

Question 15

Which of the following statements about electromagnetic waves is correct?

Accepted Answer

Correct Option: D. Solution: Electromagnetic waves are transverse waves where the electric and magnetic fields are perpendicular to each other and to the direction of propagation.

Question 16

Given a plane electromagnetic wave with electric field $E_x = E_0 \sin(kz - \omega t)$ and magnetic field $B_y = B_0 \sin(kz - \omega t)$, what is the relationship between $E_0$ and $B_0$?

Accepted Answer

Correct Option: A. Solution: The relationship between the amplitudes of the electric and magnetic fields in an electromagnetic wave is given by $E_0 = cB_0$, where $c$ is the speed of light.

Question 17

What is the purpose of introducing the displacement current in Maxwell's equations?

Accepted Answer

Correct Option: B. Solution: The displacement current was introduced by Maxwell to remove the inconsistency in Ampere's circuital law when applied to a charging capacitor.

Question 18

Which of the following correctly represents the expression for displacement current $i_d$?

Accepted Answer

Correct Option: A. Solution: The displacement current is given by $i_d = \epsilon_0 \frac{d\Phi_E}{dt}$, where $\Phi_E$ is the electric flux.

Question 19

Given a plane electromagnetic wave with an electric field amplitude $E_0 = 120 	ext{ N/C}$ and frequency $f = 50.0 	ext{ MHz}$, what is the amplitude of the magnetic field $B_0$?

Accepted Answer

Correct Option: B. Solution: The amplitude of the magnetic field is given by $B_0 = \frac{E_0}{c}$, where $c = 3 	imes 10^8 	ext{ m/s}$. Substituting the given values, $B_0 = \frac{120}{3 	imes 10^8} = 4.0 	imes 10^{-8} 	ext{ T}$.

Question 20

Which of the following devices is NOT typically associated with the use of microwaves?

Accepted Answer

Correct Option: C. Solution: X-ray machines use X-rays, not microwaves. Microwaves are used in radar systems, microwave ovens, and speed guns.

Question 21

In a plane electromagnetic wave traveling in the z-direction, how are the electric field ($E$) and magnetic field ($B$) oriented?

Accepted Answer

Correct Option: B. Solution: In a plane electromagnetic wave, the electric field ($E$) and magnetic field ($B$) are perpendicular to each other and to the direction of wave propagation.

Question 22

In a plane electromagnetic wave, the electric field ($E$) and magnetic field ($B$) are oriented in which manner relative to the direction of wave propagation?

Accepted Answer

Correct Option: C. Solution: In a plane electromagnetic wave, the electric field ($E$) and magnetic field ($B$) are perpendicular to each other and also perpendicular to the direction of wave propagation, demonstrating the transverse nature of electromagnetic waves.

Question 23

In a hypothetical scenario, an X-ray machine is set to operate at a wavelength of $1.0 	imes 10^{-10}$ m. If the speed of light is $3.0 	imes 10^8$ m/s, what is the frequency of the X-rays produced?

Accepted Answer

Correct Option: B. Solution: The frequency $f$ of X-rays can be calculated using the formula $c = \lambda f$, where $c$ is the speed of light and $\lambda$ is the wavelength. Substituting the given values, $f = \frac{3.0 	imes 10^8}{1.0 	imes 10^{-10}} = 3.0 	imes 10^{18}$ Hz.

Question 24

Maxwell introduced the concept of displacement current to resolve an inconsistency in which law?

Accepted Answer

Correct Option: C. Solution: Maxwell introduced the displacement current to correct Ampere's Circuital Law, allowing it to account for the magnetic field generated by a time-varying electric field.

Question 25

Which of the following frequency ranges is used for FM radio transmission?

Accepted Answer

Correct Option: C. Solution: The FM radio band extends from 88 MHz to 108 MHz.

Question 26

In a microwave oven, the frequency of microwaves is selected to match the resonant frequency of which molecules, thereby increasing the temperature of food?

Accepted Answer

Correct Option: B. Solution: Microwave ovens use microwaves at a frequency that matches the resonant frequency of water molecules, efficiently transferring energy and increasing the temperature of food containing water.

Question 27

Which of the following statements about X-rays is correct?

Accepted Answer

Correct Option: A. Solution: X-rays are produced by bombarding metal targets with high-energy electrons, which is why they are used in medical diagnosis and cancer treatment. However, they can damage living tissues, so overexposure must be avoided.

Question 28

What is the speed of electromagnetic waves in a vacuum?

Accepted Answer

Correct Option: A. Solution: In a vacuum, electromagnetic waves travel at $c = 3 	imes 10^8 	ext{ m/s}$, which is the speed of light.

Question 29

What is the frequency of an electromagnetic wave with a wavelength of $500 \, 	ext{nm}$ in a vacuum?

Accepted Answer

Correct Option: A. Solution: The speed of light $c$ is related to frequency $v$ and wavelength $\lambda$ by $c = v \lambda$. Solving for $v$, we have $v = c / \lambda = 3 \, 	imes \, 10^8 \, 	ext{m/s} / 500 \, 	imes \, 10^{-9} \, 	ext{m} = 6 \, 	imes \, 10^{14} \, 	ext{Hz}$.

Question 30

What is the relationship between the speed of light ($c$), the permittivity ($\varepsilon_0$), and the permeability ($\mu_0$) of free space?

Accepted Answer

Correct Option: A. Solution: The speed of light $c$ in vacuum is given by the relation $c = \frac{1}{\sqrt{\varepsilon_0 \mu_0}}$, where $\varepsilon_0$ is the permittivity and $\mu_0$ is the permeability of free space.

Question 31

What is the primary reason infrared waves are referred to as 'heat waves'?

Accepted Answer

Correct Option: C. Solution: Infrared waves are called 'heat waves' because they are absorbed by molecules such as $H_2O$ and $CO_2$, increasing their thermal motion and thus raising the temperature.

Question 32

The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is $B_0 = 510$ nT. What is the amplitude of the electric field part of the wave?

Accepted Answer

Correct Option: B. Solution: The amplitude of the electric field $E_0$ is given by $E_0 = cB_0 = 3 	imes 10^8 	imes 510 	imes 10^{-9} = 1530$ N/C.

Question 33

Which of the following is a consequence of Maxwell's equations regarding electromagnetic waves?

Accepted Answer

Correct Option: A. Solution: Maxwell's equations predict that electromagnetic waves can propagate in a vacuum as self-sustaining oscillations of electric and magnetic fields.

Question 34

What is the role of displacement current in Maxwell's equations?

Accepted Answer

Correct Option: A. Solution: Displacement current is introduced in Maxwell's equations to account for the magnetic field generated by a time-varying electric field, ensuring consistency in Ampere's circuital law.

Question 35

Which of the following is a consequence of the interaction of electromagnetic waves with matter?

Accepted Answer

Correct Option: B. Solution: Electromagnetic waves interact with matter through electric and magnetic fields that set charges in matter into oscillation.

Question 36

What is the primary reason that infrared waves are often referred to as heat waves?

Accepted Answer

Correct Option: B. Solution: Infrared waves are absorbed by water molecules, which increases their thermal motion, thus raising the temperature.

Question 37

How does the concept of displacement current contribute to the symmetry between electric and magnetic fields?

Accepted Answer

Correct Option: C. Solution: The displacement current concept contributes to the symmetry by showing that a time-varying electric field can create a magnetic field, analogous to how a time-varying magnetic field induces an electric field, as per Faraday's law.

Question 38

Which of the following equations correctly describes the relationship between the speed of light $c$, the frequency $
u$, and the wavelength $\lambda$ of an electromagnetic wave?

Accepted Answer

Correct Option: A. Solution: The speed of light $c$ is given by the product of the frequency $
u$ and the wavelength $\lambda$, i.e., $c = 
u \lambda$.

Question 39

In a parallel plate capacitor being charged, what role does the displacement current play?

Accepted Answer

Correct Option: B. Solution: The displacement current, which arises from the changing electric field between the plates of a capacitor, acts as a source of magnetic field, similar to conduction current.

Question 40

In the electromagnetic spectrum, which type of wave is primarily used for radar systems due to its short wavelength?

Accepted Answer

Correct Option: B. Solution: Microwaves, with their short wavelengths, are suitable for radar systems used in aircraft navigation.

Question 41

In the context of electromagnetic waves, what role does the displacement current play?

Accepted Answer

Correct Option: B. Solution: The displacement current generates magnetic fields, similar to conduction current, and is essential for the propagation of electromagnetic waves.

Question 42

If a plane electromagnetic wave is traveling in a vacuum with a frequency of $30 	ext{ MHz}$, what is its wavelength?

Accepted Answer

Correct Option: A. Solution: The wavelength $\lambda$ of an electromagnetic wave is given by $\lambda = \frac{c}{f}$, where $c = 3 	imes 10^8 	ext{ m/s}$ and $f = 30 	imes 10^6 	ext{ Hz}$. Thus, $\lambda = \frac{3 	imes 10^8}{30 	imes 10^6} = 10 	ext{ m}$.

Question 43

In a vacuum, an electromagnetic wave has an electric field amplitude $E_0 = 120 	ext{ N/C}$. What is the amplitude of the magnetic field $B_0$?

Accepted Answer

Correct Option: B. Solution: The amplitude of the magnetic field $B_0$ is given by $B_0 = \frac{E_0}{c}$, where $c = 3 	imes 10^8 	ext{ m/s}$ is the speed of light. Therefore, $B_0 = \frac{120}{3 	imes 10^8} = 4 	imes 10^{-7} 	ext{ T}$.

Question 44

Which part of the electromagnetic spectrum is most responsible for the greenhouse effect on Earth?

Accepted Answer

Correct Option: B. Solution: Infrared waves are absorbed by greenhouse gases, which trap heat and contribute to the greenhouse effect.

Question 45

If an electromagnetic wave is propagating in the z-direction with a frequency of 30 MHz, what is its wavelength?

Accepted Answer

Correct Option: A. Solution: The wavelength ($\lambda$) of an electromagnetic wave is given by $\lambda = \frac{c}{f}$, where $c = 3 	imes 10^8 	ext{ m/s}$ is the speed of light and $f = 30 	imes 10^6 	ext{ Hz}$. Thus, $\lambda = \frac{3 	imes 10^8}{30 	imes 10^6} = 10 	ext{ m}$.

Question 46

In the context of a charging capacitor, what role does the displacement current play?

Accepted Answer

Correct Option: B. Solution: The displacement current ensures that the calculated magnetic field is consistent, regardless of the surface used, by adding a term to Ampere's circuital law.

Question 47

In the context of electromagnetic waves, what does the equation $B_0 = \frac{E_0}{c}$ represent?

Accepted Answer

Correct Option: B. Solution: The equation $B_0 = \frac{E_0}{c}$ represents the relationship between the magnitudes of electric and magnetic fields in an electromagnetic wave propagating in a vacuum, where $c$ is the speed of light.

Question 48

An electromagnetic wave is propagating in the z-direction. If the electric field vector is along the x-axis, what is the direction of the magnetic field vector?

Accepted Answer

Correct Option: A. Solution: In an electromagnetic wave, the electric field, magnetic field, and direction of propagation are mutually perpendicular. Hence, if the electric field is along the x-axis and the wave propagates in the z-direction, the magnetic field must be along the y-axis.

Question 49

What is the speed of electromagnetic waves in a vacuum, and how is it derived?

Accepted Answer

Correct Option: A. Solution: The speed of electromagnetic waves in a vacuum is $3 	imes 10^8 	ext{ m/s}$, derived from the equation $c = \frac{1}{\sqrt{\mu_0 \varepsilon_0}}$, where $\mu_0$ is the permeability and $\varepsilon_0$ is the permittivity of free space.

Question 50

What is the primary reason that electromagnetic waves can propagate through the vacuum of space?

Accepted Answer

Correct Option: B. Solution: Electromagnetic waves consist of oscillating electric and magnetic fields that regenerate each other, allowing them to propagate through the vacuum without a medium.

Question 51

For a plane electromagnetic wave propagating along the z-axis, the electric field $E_x$ is given by $E_x = E_0 \sin(kz - \omega t)$. What is the expression for the magnetic field $B_y$?

Accepted Answer

Correct Option: B. Solution: The magnetic field $B_y$ is in phase with the electric field $E_x$, hence $B_y = B_0 \sin(kz - \omega t)$.

Question 52

How does the introduction of displacement current affect the symmetry of Maxwell's equations?

Accepted Answer

Correct Option: B. Solution: The introduction of displacement current enhances the symmetry of Maxwell's equations by allowing the time-varying electric field to generate a magnetic field, similar to how a time-varying magnetic field generates an electric field.

Question 53

Which of the following laws describes the generation of a magnetic field due to a time-varying electric field?

Accepted Answer

Correct Option: C. Solution: Maxwell's Displacement Current describes the generation of a magnetic field due to a time-varying electric field, resolving the inconsistency in Ampere's Circuital Law.

Question 54

What is the primary method of production for microwaves?

Accepted Answer

Correct Option: B. Solution: Microwaves are primarily produced using klystron or magnetron valves, which are special vacuum tubes.

Question 55

In a plane electromagnetic wave traveling in the z-direction, how are the electric and magnetic fields oriented?

Accepted Answer

Correct Option: C. Solution: In a plane electromagnetic wave, the electric and magnetic fields are perpendicular to each other and to the direction of wave propagation.

Question 56

Why is the displacement current concept crucial for the consistency of Maxwell's equations?

Accepted Answer

Correct Option: D. Solution: The displacement current is crucial for maintaining the symmetry between electric and magnetic fields in Maxwell's equations, allowing time-varying electric fields to produce magnetic fields.

Question 57

In a charging capacitor, which type of current exists between the plates and is responsible for maintaining the continuity of the magnetic field?

Accepted Answer

Correct Option: B. Solution: In a charging capacitor, displacement current exists between the plates to maintain the continuity of the magnetic field, as the conduction current exists in the wires.

Question 58

Consider a plane electromagnetic wave propagating along the z-axis. If the electric field is given by $E_x = E_0 \sin(kz - \omega t)$, what is the expression for the magnetic field component $B_y$?

Accepted Answer

Correct Option: B. Solution: For a plane electromagnetic wave propagating along the z-axis, the electric and magnetic fields are in phase. Therefore, $B_y = B_0 \sin(kz - \omega t)$ is the correct expression.

Question 59

In electromagnetic waves, what is the relationship between the magnitudes of the electric field $E_0$ and the magnetic field $B_0$ in a vacuum?

Accepted Answer

Correct Option: B. Solution: In a vacuum, the relationship between the electric field $E_0$ and the magnetic field $B_0$ is given by $E_0 = c B_0$, where $c$ is the speed of light.

Question 60

According to the Ampere-Maxwell Law, what is the expression for the total current passing through a surface?

Accepted Answer

Correct Option: A. Solution: The total current is the sum of the conduction current $i_c$ and the displacement current $i_d$, as given by the Ampere-Maxwell Law.

Question 61

What is the primary condition for the generation of electromagnetic waves according to Maxwell's theory?

Accepted Answer

Correct Option: C. Solution: According to Maxwell's theory, accelerated charges are necessary for the generation of electromagnetic waves, as they produce oscillating electric and magnetic fields.

Question 62

An electromagnetic wave is traveling in vacuum. If the electric field amplitude is known to be $E_0 = 300 	ext{ V/m}$, what is the magnetic field amplitude $B_0$?

Accepted Answer

Correct Option: C. Solution: Using the relation $E_0 = cB_0$, where $c = 3 	imes 10^8 	ext{ m/s}$, we find $B_0 = \frac{E_0}{c} = \frac{300}{3 	imes 10^8} = 1 	imes 10^{-8} 	ext{ T}$.

Question 63

In the context of electromagnetic waves, what is the significance of Hertz's experiment in 1887?

Accepted Answer

Correct Option: A. Solution: Hertz's experiment was pivotal in demonstrating the existence of electromagnetic waves, thus confirming the theoretical predictions made by Maxwell.

Question 64

Which of the following statements correctly describes the role of displacement current in Maxwell's equations?

Accepted Answer

Correct Option: A. Solution: Displacement current is introduced to account for the magnetic field generated by a time-varying electric field, ensuring the consistency of Ampere's law in the presence of capacitors.

Electromagnetic Waves

Learning Objectives

Revision Notes & Summary

Chapter Eight: Electromagnetic Waves

8.1 Introduction

8.3 Key Concepts

8.4 Electromagnetic Spectrum

Examples

Important Notes

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips

Common Pitfalls

Exam Tips

AI Learning Assistant

Practice Test – MCQs, True/False

Experience the StudyTunnel Method

Step 1: Chapter Practice

Step 2: Term Boss Exam

Step 3: Redemption Arena

Practice, Analyze & Improve 🚀

Multiple Choice Questions

Q1.Which of the following statements is true about the production of electromagnetic waves?

Correct Answer: C

Q2.In the generalised Ampere-Maxwell law, which of the following represents the total current linked with a surface?

Correct Answer: C

Q3.In the context of the displacement current, what is the significance of the term ε0dΦEdt\varepsilon_0 \frac{d\Phi_E}{dt}ε0​dtdΦE​​?

Correct Answer: A

Q4.Which of Maxwell's equations in vacuum describes the absence of magnetic monopoles?

Correct Answer: B

Q5.If a plane electromagnetic wave travels in vacuum along the z-direction, what can be said about the directions of its electric and magnetic field vectors?

Correct Answer: B

Q6.Which of the following statements correctly describes the production of radio waves?

Correct Answer: A

Q7.In the context of Maxwell's equations, what is the significance of the Ampere-Maxwell law?

Correct Answer: C

Q8.How does the speed of electromagnetic waves change when they travel through a medium?

Correct Answer: C

Q9.In an electromagnetic wave traveling in vacuum, the ratio of the magnitudes of the electric field E0E_0E0​ to the magnetic field B0B_0B0​ is equal to the speed of light ccc. If the electric field amplitude is 120 N/C120 \, \text{N/C}120N/C, what is the amplitude of the magnetic field?

Correct Answer: B

Q10.In the context of electromagnetic waves, what is the significance of the displacement current?

Correct Answer: A

Q11.In a vacuum, the electric field amplitude E0E_0E0​ and magnetic field amplitude B0B_0B0​ of an electromagnetic wave are related by which equation?

Correct Answer: B

Q12.During the charging of a capacitor, how does the displacement current compare to the conduction current?

Correct Answer: C

Q13.Microwaves are used in radar systems due to their specific properties. Which of the following is a reason for their suitability in radar applications?

Correct Answer: B

Q14.Which of the following is NOT a common use of infrared waves?

Correct Answer: C

Q15.Which of the following statements about electromagnetic waves is correct?

Correct Answer: D

Q16.Given a plane electromagnetic wave with electric field Ex=E0sin⁡(kz−ωt)E_x = E_0 \sin(kz - \omega t)Ex​=E0​sin(kz−ωt) and magnetic field By=B0sin⁡(kz−ωt)B_y = B_0 \sin(kz - \omega t)By​=B0​sin(kz−ωt), what is the relationship between E0E_0E0​ and B0B_0B0​?

Correct Answer: A

Q17.What is the purpose of introducing the displacement current in Maxwell's equations?

Correct Answer: B

Q18.Which of the following correctly represents the expression for displacement current idi_did​?

Correct Answer: A

Q19.Given a plane electromagnetic wave with an electric field amplitude E0=120 N/CE_0 = 120 \text{ N/C}E0​=120 N/C and frequency f=50.0 MHzf = 50.0 \text{ MHz}f=50.0 MHz, what is the amplitude of the magnetic field B0B_0B0​?

Correct Answer: B

Q20.Which of the following devices is NOT typically associated with the use of microwaves?

Correct Answer: C

Q21.In a plane electromagnetic wave traveling in the z-direction, how are the electric field (EEE) and magnetic field (BBB) oriented?

Correct Answer: B

Q22.In a plane electromagnetic wave, the electric field (EEE) and magnetic field (BBB) are oriented in which manner relative to the direction of wave propagation?

Correct Answer: C

Q23.In a hypothetical scenario, an X-ray machine is set to operate at a wavelength of 1.0×10−101.0 \times 10^{-10}1.0×10−10 m. If the speed of light is 3.0×1083.0 \times 10^83.0×108 m/s, what is the frequency of the X-rays produced?

Correct Answer: B

Q24.Maxwell introduced the concept of displacement current to resolve an inconsistency in which law?

Correct Answer: C

Q25.Which of the following frequency ranges is used for FM radio transmission?

Correct Answer: C

Q26.In a microwave oven, the frequency of microwaves is selected to match the resonant frequency of which molecules, thereby increasing the temperature of food?

Correct Answer: B

Q27.Which of the following statements about X-rays is correct?

Correct Answer: A

Q28.What is the speed of electromagnetic waves in a vacuum?

Correct Answer: A

Q29.What is the frequency of an electromagnetic wave with a wavelength of 500 nm500 \, \text{nm}500nm in a vacuum?

Correct Answer: A

Q30.What is the relationship between the speed of light (ccc), the permittivity (ε0\varepsilon_0ε0​), and the permeability (μ0\mu_0μ0​) of free space?