Electromagnetic Waves Mock Test

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Quiz: Electromagnetic Waves – Progressive Test
Total questions: 400
Questions in this round: 50
Time allotted: 70 minutes
Pass score: 60%
Total rounds: 8
Current round: 1^st
Rounds passed: 0 / 8
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Rounds attempted: 0

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Quiz: Electromagnetic Waves – Certificate Challenge
Total questions: 400
Questions to attempt: 100 random
Time allotted: 100 minutes
Certificate pass score: 70%
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Progressive Test — Guest First Round

Electromagnetic Waves – Progressive Test

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1 / 50

1. Two plane electromagnetic waves in vacuum have magnetic-field amplitudes and . Their electric-field amplitudes satisfy

2 / 50

2. Assertion: In a charging capacitor, Maxwell's correction makes Ampere's law independent of the surface chosen for the same boundary loop.
Reason: The displacement-current term accounts for the changing electric flux through a surface between the plates.

a) Both Assertion and Reason are true, and Reason explains Assertion

b) Assertion is false, but Reason is true

c) Both Assertion and Reason are true, but Reason does not explain Assertion

d) Assertion is true, but Reason is false

3 / 50

3. A detector is placed in vacuum where a plane electromagnetic wave has at one instant. The same instant has electric energy density , magnetic energy density , and magnetic field . The correct set is

a) and

b) and

c) and always

d) and

4 / 50

4. An electromagnetic wave in vacuum has wavelength , while another has wavelength . The frequency of the second wave is

a) equal to the frequency of the first

b) times the frequency of the first

c) times the frequency of the first

d) times the frequency of the first

5 / 50

5. A radiation region is described as having the highest frequency and shortest wavelength among common electromagnetic spectrum regions. It is most likely

a) radio waves

b) visible red light

c) gamma rays

d) infrared radiation

6 / 50

6. A comparison is made among radio waves, visible light, X-rays, and gamma rays in vacuum. The correct common feature is that all of them

a) travel at speed in vacuum

b) have the same wavelength in vacuum

c) have identical ionising ability in matter

d) have the same frequency in vacuum

7 / 50

7. Study the table and select the row that gives a suitable atmospheric interaction.

Row	Radiation region	Atmospheric context
P	Ultraviolet	Much harmful ultraviolet is absorbed by ozone
Q	Infrared	No atmospheric gas can absorb it under any condition
R	Microwaves	Never used for satellite communication
S	Visible light	Completely blocked by the atmosphere at all times

a) Row Q

b) Row P

c) Row R

d) Row S

8 / 50

8. Study the table and identify the row that contains an unsuitable conclusion.

Row	Situation	Conclusion
P	Stationary charge	Electric field exists
Q	Steady moving charge	Electric and magnetic fields can be associated
R	Accelerated charge	Electromagnetic radiation can be produced
S	Charge at rest	Radio waves are radiated continuously

a) Row P

b) Row Q

c) Row S

d) Row R

9 / 50

9. A statement says, "In an electromagnetic wave, and are in phase, so they must be parallel." The statement is

a) valid because perpendicular fields must be out of phase

b) invalid because phase timing differs from field direction

c) valid because one field must lag the other by

d) invalid because and are parallel

10 / 50

10. A radiation has a long wavelength, low photon energy, and is useful for broadcasting. It is most likely

a) an X-ray

b) a radio wave

c) ultraviolet radiation

d) a gamma ray

11 / 50

11. In the quantity , the subscript indicates that it is related to

a) frequency

b) magnetic flux

c) electric flux

d) conduction current

12 / 50

12. An electromagnetic wave in vacuum has frequency . Taking , its wavelength is

13 / 50

13. Consider the following charge situations.
Statement I: A stationary charge produces an electric field.
Statement II: A steady moving charge produces electric and magnetic fields.
Statement III: An accelerated charge can produce electromagnetic waves.

a) II and III only

b) I and II only

c) I, II and III

d) I and III only

14 / 50

14. A photosensitive metal surface emits electrons when ultraviolet light falls on it, but not when low-frequency red light of the same weak intensity is used. The most suitable reason is that

a) red light travels slower than ultraviolet in vacuum

b) ultraviolet photons have higher energy

c) ultraviolet radiation has no electric-field component

d) red light has shorter wavelength than ultraviolet

15 / 50

15. Ozone in the upper atmosphere is important because it absorbs much of the harmful part of

a) ultraviolet radiation

b) radio waves

c) microwaves

d) infrared radiation from remote controls only

16 / 50

16. Study the order table and select the row that is correctly arranged from longer wavelength to shorter wavelength.

Row	Order
P	radio waves microwaves infrared visible light
Q	visible light infrared microwaves radio waves
R	X-rays ultraviolet visible light infrared
S	gamma rays radio waves visible light ultraviolet

a) Row S

b) Row P

c) Row R

d) Row Q

17 / 50

17. A radiation detector receives two electromagnetic waves in vacuum. Wave P has , and wave Q has . Using only the wavelength trend, wave Q is more likely to be

a) a gamma ray or very high-frequency X-ray

b) a microwave with lower frequency than P

c) an infrared wave with longer wavelength than P

d) a radio wave with the same photon energy as wave P

18 / 50

18. Read the passage below

In a conducting antenna, charges are driven back and forth rapidly. The changing motion of these charges produces electromagnetic radiation that travels away from the antenna.

The radiation leaves the antenna mainly because the charges are

a) neutralized completely

b) accelerated

c) converted into sound waves

d) stationary

19 / 50

19. Match the basic field symbols with their usual meanings.

Column I	Column II
P.	1. Magnetic field
Q.	2. Electric field
R.	3. Wavelength
S.	4. Frequency

a) P-2, Q-1, R-4, S-3

b) P-1, Q-2, R-3, S-4

c) P-3, Q-4, R-2, S-1

d) P-2, Q-1, R-3, S-4

20 / 50

20. A radio transmitting antenna works because charges in it are made to

a) oscillate and therefore accelerate

b) move with constant speed in one direction only

c) disappear into the surrounding air

d) remain permanently at rest

21 / 50

21. Study the table and select the row that gives the most suitable application-safety pairing.

Row	Radiation	Useful application	Safety concern
P	Gamma rays	Cancer therapy or sterilisation	Ionising and highly penetrating
Q	Radio waves	Medical bone imaging	Strong ionisation at ordinary broadcast levels
R	Infrared	Nuclear cancer therapy	Highest photon energy in the spectrum
S	Microwaves	Radioactive nuclear decay	Always more penetrating than gamma rays

a) Row R

b) Row S

c) Row P

d) Row Q

22 / 50

22. A wave has and . The speed calculated from these data is

23 / 50

23. During an interval, the charge on an ideal parallel-plate capacitor changes from to . The change in electric flux is

24 / 50

24. A plane region in space has a time-varying electric field. According to the Maxwell-correction idea, the immediate magnetic-field-related effect is that the changing electric field can

a) change frequency into wavelength

b) produce magnetic field circulation

c) remove all electric flux from the region

d) create isolated magnetic poles

25 / 50

25. A claim says, "Visible light is the central and largest part of the electromagnetic spectrum because humans can see it." The claim is

a) invalid because visible light is not electromagnetic radiation

b) valid because human vision defines the whole spectrum

c) valid because all invisible waves have zero frequency

d) invalid because visible light is only a narrow spectrum region

26 / 50

26. An electromagnetic wave has . Its ordinary frequency is

27 / 50

27. A statement says, "Once produced, an electromagnetic wave needs a material medium to keep regenerating its fields." The statement is wrong because

a) electromagnetic waves carry no field energy

b) electric and magnetic fields cannot exist in vacuum

c) electromagnetic waves are really pressure waves in space

d) the wave fields are mutually linked during propagation

28 / 50

28. At a fixed time, the expression varies from point to point because of

a) the coordinate

b) the constant alone

c) the current

d) the electric flux only

29 / 50

29. A claim says, "Since , a larger magnetic-field amplitude in the same vacuum plane wave family means a proportionally larger electric-field amplitude." This claim is

a) correct because

b) wrong because

c) wrong because and are always equal

d) correct only if

30 / 50

30. Radio waves are commonly produced in communication systems by

a) sudden stopping of high-energy electrons in X-ray tubes

b) only nuclear radioactive decay

c) accelerated charges in conducting antennas

d) stationary charges kept permanently at rest

31 / 50

31. Electromagnetic radiation is called ionising when it has enough photon energy to

a) remove electrons from atoms or molecules

b) travel at a speed greater than in vacuum

c) lose its electric and magnetic fields

d) become a sound wave in air

32 / 50

32. A plane electromagnetic wave in vacuum has at a particular point and instant. Using , the magnetic field magnitude at that point and instant is

a) maximum

33 / 50

33. A hot metal rod first appears dull red as it is heated and also emits invisible radiation before it glows visibly. The invisible radiation mainly belongs to the

a) infrared region

b) X-ray region

c) gamma-ray region

d) radio-wave region only

34 / 50

34. A learner uses for a vacuum electromagnetic wave. The error in this relation is that it

a) reverses the correct amplitude relation

b) correctly gives the magnetic field in

c) is valid only for radio waves

d) applies only when

35 / 50

35. Gamma rays are most commonly associated with

a) oscillating charges in a radio antenna

b) thermal radiation from room-temperature objects only

c) nuclear transitions and radioactive processes

d) heating of food by water molecules

36 / 50

36. A parallel-plate capacitor has plate area , charge , and electric field . The electric flux through the plate area between the plates is

37 / 50

37. Consider the following statements about displacement current.
Statement I: It can exist in a vacuum region if electric flux changes with time.
Statement II: It is always due to free electrons crossing a metallic conductor.
Statement III: It can contribute to magnetic-field circulation.

a) II and III only

b) I, II and III

c) I and III only

d) I and II only

38 / 50

38. Microwaves are useful in radar systems mainly because they

a) have lower frequency than all radio waves

b) can be directed in narrow beams and reflected by objects

c) are the only electromagnetic waves that cannot travel in vacuum

d) are longitudinal pressure waves

39 / 50

39. Electromagnetic waves can show reflection, refraction, interference, diffraction, and polarisation. This set of behaviours shows that they

a) are only streams of charges

b) require air for all propagation

c) behave as waves

d) have no transverse character

40 / 50

40. A wave has frequency . Its time period is

41 / 50

41. A receiving antenna detects a radio wave because the wave's electric field can

a) change the radio wave into a sound wave before detection

b) make charges in the antenna oscillate

c) remove the need for any electric current in the receiver circuit

d) convert the antenna into a permanent magnet

42 / 50

42. The relation for an ideal parallel-plate capacitor shows that the change in flux during charging is caused most directly by

a) change in the frequency

b) change in the magnetic flux

c) change in the plate charge

d) change in the speed of light

43 / 50

43. Match each current-related idea with its proper description.

Column I	Column II
P.	1. Caused by changing electric flux
Q.	2. Caused by drift of charge carriers
R.	3. Definition of displacement current
S.	4. Total current-like term in Ampere-Maxwell law

a) P-2, Q-1, R-3, S-4

b) P-1, Q-2, R-3, S-4

c) P-4, Q-1, R-2, S-3

d) P-2, Q-3, R-1, S-4

44 / 50

44. Study the comparison table and identify the row that gives the proper distinction.

Row	Conduction current	Displacement current
P	Due to drifting charge carriers	Due to changing electric flux
Q	Due to changing electric flux	Due to drifting charge carriers only
R	Exists only in vacuum	Exists only in metallic wires
S	Measured in	Measured in

a) Row Q

b) Row P

c) Row R

d) Row S

45 / 50

45. Sunlight warms a surface on Earth after travelling through space. This is possible because electromagnetic waves

a) carry only magnetic flux but no energy

b) require air molecules between the Sun and Earth

c) are identical to sound waves

d) carry energy even through vacuum

46 / 50

46. A plane electromagnetic wave is written as and . The wave propagates along

47 / 50

47. Study the table and identify the row that correctly compares the two ends of the electromagnetic spectrum.

Row	Region	Relative frequency	Relative wavelength
P	Radio waves	Low	Long
Q	Gamma rays	Low	Short
R	Radio waves	High	Short
S	Gamma rays	High	Long

a) Row S

b) Row Q

c) Row R

d) Row P

48 / 50

48. A graph-like spectrum line is marked from low frequency on the left to high frequency on the right. The region at the far right is also marked "highest photon energy." That region is best identified as

a) radio waves

b) infrared radiation

c) gamma rays

d) visible red light

49 / 50

49. A capacitor is being charged through a wire. At a certain instant, the wire current is , and the charge on each plate is still increasing. The region between the plates is most likely to contain

a) a changing electric field linked with changing electric flux

b) a steady electric field and no changing flux

c) a conduction current equal to electron drift through the dielectric

d) no electric field because current cannot cross the gap

50 / 50

50. A plane electromagnetic wave in vacuum has , where . At a point where , the electric-field magnitude at the same point and instant is

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Electromagnetic Waves Mock Test – Class 12 Physics

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