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All questions of Electromagnetic Waves for NEET Exam

Which region in the electromagnetic spectrum will have the highest speed?
  • a)
    Radio
  • b)
    Visible
  • c)
    All the regions have same speed
  • d)
    Microwaves
Correct answer is option 'C'. Can you explain this answer?

Alok Mehta answered
The entire electromagnetic spectrum, from the lowest to the highest frequency (longest to shortest wavelength), includes all radio waves (e.g., commercial radio and television, microwaves, radar), infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
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Which region in the electromagnetic spectrum has the highest frequency?
  • a)
    Frequency is same for the complete spectrum
  • b)
    Gamma Radiation Region
  • c)
    Radio
  • d)
    Visible
Correct answer is option 'B'. Can you explain this answer?

Shaik Khaja Azeem Ali answered
A gamma ray or gamma radiation is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy

Infrared waves are produced by
  • a)
    Permanent magnets
  • b)
    dipole oscillations
  • c)
    static charges
  • d)
    all hot bodies and molecules
Correct answer is option 'D'. Can you explain this answer?

Yashika Singh answered
Option(d)becoz---> infrared radiation is heat or thermal radiation, any object which has a temperature radiates in the infrared. Even objects that we think of as being very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to radiate visible light, it will emit most of its energy in the infrared

Weather forecasting uses
  • a)
    Visible Rays
  • b)
    Micro waves
  • c)
    Infra red Rays
  • d)
    Gamma Rays
Correct answer is option 'C'. Can you explain this answer?

Nandini Iyer answered
It's an infrared sensor that reads temperatures.This sensor allows satellites to measure the amount of energy radiated by Earth's surface, clouds, oceans, air, and so on. Infrared sensors can be used at night—a helpful feature for forecasters, considering that the imager can only pick up data during daylight hours.

Do EM waves need a medium to travel through?
  • a)
    No
  • b)
    Yes
  • c)
    ether is required
  • d)
    None of the above
Correct answer is option 'A'. Can you explain this answer?

Gopikas S answered
The electromagnetic waves are not mechanical waves. There are vibrations of electric vector and magnetic vector in them. These vibrations do not need any particles present in the medium for their propagation. That's why electromagnetic waves do not require any medium for propagation.

Infra red rays are used
  • a)
    radar systems
  • b)
    In green house to keep plants warm
  • c)
    To treat muscular pain
  • d)
    Both b and c
Correct answer is option 'D'. Can you explain this answer?

Niki Niki answered
Infra red rays are basically heat radiation it gives warmth which support the plant growth. It also helps in treating muscle pain in the same way we use hot water massage for muscle cramps. Hope it helps:)

The physical properties of electromagnetic waves are decided by their
  • a)
    Method of excitation
  • b)
    Wavelength
  • c)
    Frequency
  • d)
    Amplitude
Correct answer is option 'B'. Can you explain this answer?

Rajat Patel answered
These electric and magnetic waves travel perpendicular to each other and have certain characteristics, including amplitude, wavelength, and frequency. General Properties of all electromagnetic radiation: Electromagnetic radiation can travel through empty space.

The intensity of a plane electromagnetic wave is proportional to
  • a)
    1/ Electric field squared
  • b)
    Electric field cubed
  • c)
    Electric field
  • d)
    Electric field squared
Correct answer is option 'D'. Can you explain this answer?

Sreemoyee Sengupta answered
Explanation:

Intensity is defined as the rate at which energy is transmitted through a unit area perpendicular to the direction of propagation of the wave. The intensity of a plane electromagnetic wave is proportional to the square of the amplitude of its electric field.

I = 1/2εcE²

where I represents the intensity, ε represents the permittivity of free space, c represents the speed of light, and E represents the amplitude of the electric field.

To find the proportionality between the intensity and the electric field, we can simplify the above equation as follows:

I ∝ E²

Therefore, the correct option is D, i.e., the intensity of a plane electromagnetic wave is proportional to the square of its electric field.

Conclusion:

The intensity of a plane electromagnetic wave is proportional to the square of its electric field. This relationship is important in various applications of electromagnetic waves, such as in the design of antennas and in the measurement of electromagnetic radiation.

Tanning of the skin in sunlight is due to
  • a)
    UV radiation
  • b)
    visible light
  • c)
    infrared
  • d)
    cosmic rays
Correct answer is option 'A'. Can you explain this answer?

Ayaan Madhukar answered
When we get a tan, what is actually happening is that the melanocytes are producing melanin pigment in reaction to ultraviolet light in sunlight...

So, correct answer is "UV radiation"...

$$Hope it's help... $$

Electromagnetic waves constitute of
  • a)
    Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are at 30 degrees to the direction of propagation.
  • b)
    Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to the direction of propagation.
  • c)
    Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are parallell to the direction of propagation.
  • d)
    Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are at 60 degrees to the direction of propagation.
Correct answer is option 'B'. Can you explain this answer?

Suresh Iyer answered
Maxwell predicted that an accelerated charge produces a sinusoidal time varying magnetic field, which in turn produces a sinusoidal time varying electric field. These two fields are mutually perpendicular to each other and sources of each other. They (fields) form an electromagnetic wave i.e. the wave that is propagated by simultaneous periodic variations of electric field and magnetic field intensity.

Comparing X-rays and Gamma rays
  • a)
    Gamma rays are less penetrating than X-rays
  • b)
    Gamma rays have larger wavelength than X-rays
  • c)
    Gamma rays have more speed than X-rays
  • d)
    Gamma rays have more energy than X-rays
Correct answer is option 'D'. Can you explain this answer?

Preeti Iyer answered
Gamma-ray photons have the highest energy in the EMR spectrum and their waves have the shortest wavelength. Scientists measure the energy of photons in electron volts (eV). X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-ray photons generally have energies greater than 100 keV.

Oscillating circuits produce
  • a)
    Radio frequencies
  • b)
    Power frequencies
  • c)
    Microwaves
  • d)
    Ultra violet Rays
Correct answer is option 'B'. Can you explain this answer?

Rajeev Sen answered
The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in an electric power grid transmitted from a power station to the end-user.An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz.

A signal emitted by an antenna from a certainpoint can be received at another point of thesurface in the form of                [1993]
  • a)
    sky wave
  • b)
    ground wave
  • c)
    sea wave
  • d)
    both a and b
Correct answer is option 'D'. Can you explain this answer?

Ramesh Chand answered
Sea waves travel in straight line thus, they can only be used for in line communication . Whereas sky waves and ground waves are used for larger distances . Therefore , option D is the correct answer.

Without the concept of displacement current it is not possible to correctly apply Ampere’s law on a path parallel to the plates of parallel plate capacitor C in
  • a)
    the region leading to plate 2
  • b)
    the region leading to plate 1
  • c)
    the region between the plates
  • d)
    the region between source and the plates
Correct answer is option 'C'. Can you explain this answer?

Rishika Patel answered
The Importance of Displacement Current in Applying Ampere's Law in a Parallel Plate Capacitor

Introduction:
In electromagnetism, Ampere's law is an important equation that relates the magnetic field to the electric current that produces it. However, when dealing with certain situations, such as a parallel plate capacitor, the application of Ampere's law requires the concept of displacement current to be included for accurate results. In this response, we will discuss why displacement current is necessary in applying Ampere's law in a parallel plate capacitor.

Parallel Plate Capacitor:
A parallel plate capacitor is a simple device consisting of two parallel plates separated by a distance, with a potential difference applied across them. When a capacitor is charged, an electric field is created between the plates, which stores energy in the form of electrostatic potential energy.

Ampere's Law:
Ampere's law states that the integral of the magnetic field around a closed loop is equal to the current passing through the loop. Mathematically, this can be expressed as:

∮B⋅dl=μ0Ienc

Where B is the magnetic field, dl is an element of the path around the loop, Ienc is the current passing through the loop, and μ0 is the permeability of free space.

Displacement Current:
Displacement current is a concept introduced by James Clerk Maxwell to account for the changing electric field in a region of space. When a capacitor is charging or discharging, the electric field between the plates is changing, which creates a displacement current. This current does not involve the flow of charge carriers, but rather the changing electric field itself.

Importance of Displacement Current in a Parallel Plate Capacitor:
When applying Ampere's law to a path parallel to the plates of a parallel plate capacitor, the displacement current must be included to obtain accurate results. This is because the electric field between the plates is changing, which creates a magnetic field that contributes to the total magnetic field around the loop. Without considering the displacement current, Ampere's law would only account for the current flow through the wires, ignoring the changing electric field between the plates.

Conclusion:
In conclusion, the concept of displacement current is necessary for accurately applying Ampere's law in a parallel plate capacitor. By including the displacement current, the changing electric field between the plates is accounted for, allowing for a more complete understanding of the magnetic field around the loop.

State the part of the electromagnetic spectrum to which 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift)..Belongs
  • a)
    Visible
  • b)
    Ultraviolet
  • c)
    Microwave
  • d)
    Radio (short wavelength end)
Correct answer is option 'D'. Can you explain this answer?

Amar Choudhary answered
The Electromagnetic Spectrum and 1057 MHz Radiation

The electromagnetic spectrum is a range of all types of electromagnetic radiation. It includes various forms of energy such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Each of these forms of energy has a specific frequency and wavelength.

1057 MHz is a specific frequency of radiation that is known as the Lamb shift. This radiation arises due to the interaction between an electron and a proton in a hydrogen atom. It is a very low-frequency radiation, and it belongs to the radio wave part of the electromagnetic spectrum.

Therefore, the correct answer to the given question is option D, i.e., radio (short wavelength end).

In summary, the Lamb shift radiation with a frequency of 1057 MHz belongs to the radio wave part of the electromagnetic spectrum.

Radioactive decay of the nucleus leads to the emission of
  • a)
    visible light
  • b)
    gamma rays
  • c)
    radio waves
  • d)
    microwaves
Correct answer is option 'B'. Can you explain this answer?

Rounak Goyal answered
The emission of gamma rays does not alter the number of protons or neutrons in the nucleus but instead has the effect of moving the nucleus from a higher to a lower energy state (unstable to stable). Gamma ray emission frequently follows beta decay, alpha decay, and other nuclear decay processes.

Which one of the following electromagneticradiations has the smallest wavelength? [1994]
  • a)
    ultraviolet waves
  • b)
    X-rays
  • c)
    γ-rays
  • d)
    microwaves
Correct answer is option 'C'. Can you explain this answer?

Krish Chakraborty answered
Rays  -    Wavelength
[Range in m]
X-rays    -  1 × 10–11 to 3 × 10–8
γ-rays     -  6 × 10–14 to 1 × 10–11
Microwaves    -  10–3 to 0.3
Radiowaves    -  10 to 104

Plane electromagnetic waves are
  • a)
    Shock waves
  • b)
    transverse waves
  • c)
    Standing waves
  • d)
    longitudinal waves
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
E is the electric field vector, and B is the magnetic field vector of the EM wave. For electromagnetic waves E and B are always perpendicular to each other and perpendicular to the direction of propagation. Electromagnetic waves are transverse waves. The wave number is k = 2π/λ, where λ is the wavelength of the wave.

Choose the correct sequence of the radiation sources in increasing order of the wavelength of electromagnetic waves produced by them.
  • a)
    X-ray tube, Magnetron valve, Radioactive source, Sodium lamp
  • b)
    Radioactive source, X-ray tube, Sodium lamp, Magnetron valve
  • c)
    X-ray tube, Magnetron valve, Sodium lamp, Radioactive source
  • d)
    Magnetron valve, Sodium lamp, X-ray tube, Radioactive source
Correct answer is option 'B'. Can you explain this answer?

Varun Chakraborty answered
Understanding Electromagnetic Radiation Sources
Electromagnetic waves vary in wavelength across different sources. To comprehend the correct order of wavelengths produced by various radiation sources, we can analyze each option provided.
Types of Radiation Sources:
- Radioactive Source: Emits gamma rays, which have very short wavelengths (high frequency).
- X-ray Tube: Produces X-rays with shorter wavelengths than visible light but longer than gamma rays.
- Sodium Lamp: Emits light in the visible spectrum, specifically in the yellow-orange range, with longer wavelengths than X-rays.
- Magnetron Valve: Primarily used in microwave ovens, it generates microwaves with even longer wavelengths than visible light.
Wavelength Order from Shortest to Longest:
- Gamma Rays (from Radioactive Source)
- X-rays (from X-ray Tube)
- Visible Light (from Sodium Lamp)
- Microwaves (from Magnetron Valve)
Correct Sequence Explained:
In option B, the order is:
1. Radioactive Source: Produces the shortest wavelengths (gamma rays).
2. X-ray Tube: Produces X-rays, which are longer than gamma rays but shorter than visible light.
3. Sodium Lamp: Emits visible light with longer wavelengths.
4. Magnetron Valve: Produces microwaves, which have the longest wavelengths in this grouping.
This sequence follows the increasing order of wavelengths, confirming that option B is indeed the correct answer.
Conclusion:
Understanding the properties of each radiation source helps in determining the correct sequence of electromagnetic wave wavelengths. This knowledge is essential for various applications in physics and medical imaging, especially relevant in NEET preparation.

The electromagnetic waves ranging in frequencies between 1 GHz and 300 GHz are called _______
  • a)
    Radio waves
  • b)
    Microwaves
  • c)
    Infrared waves
  • d)
    Light waves
Correct answer is option 'B'. Can you explain this answer?

Lead Academy answered
Option 2 : Microwaves
Concept:
  • Frequencies range of Radio waves:  3KHz to 300GHz
  • Frequencies range of Micro waves:  1GHz to 300GHz
  • Frequencies range of Infrared waves:  300GHz to 400THz
  • Frequencies range of light waves:  430THz to 750THz

Plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is 30 MHz, its wavelength is
  • a)
    13 m
  • b)
    12 m
  • c)
    11 m
  • d)
    10 m
Correct answer is option 'D'. Can you explain this answer?

Aarya Khanna answered
Electromagnetic wave and its properties

An electromagnetic wave is a disturbance that travels through space, created by the motion of electric charges. It consists of two perpendicular waves - the electric field and the magnetic field, which are also perpendicular to the direction of wave propagation. Electromagnetic waves do not require a medium for their propagation and can travel through a vacuum.

Formula for wavelength

The wavelength (λ) of an electromagnetic wave is the distance between two consecutive points on the wave that are in phase. It is related to the frequency (f) of the wave and the speed of light (c) in vacuum by the formula:

λ = c/f

Where λ is the wavelength in meters, c is the speed of light in meters per second, and f is the frequency in Hertz.

Calculation

Given that the frequency of the electromagnetic wave is 30 MHz, we can convert it to units of Hertz by multiplying it by 10^6. Therefore, f = 30 × 10^6 Hz.

The speed of light in vacuum is a constant value of 3 × 10^8 m/s.

Substituting the values in the formula for wavelength, we get:

λ = c/f = 3 × 10^8 / (30 × 10^6) = 10 m

Therefore, the wavelength of the electromagnetic wave is 10 meters.

Conclusion

The correct answer is option D, i.e. the wavelength of the electromagnetic wave with a frequency of 30 MHz is 10 meters.

According to Maxwell’s equations
  • a)
    time-varying magnetic field vanishes in electric field
  • b)
    time-varying magnetic field produce as a static electric field
  • c)
    time-varying magnetic field acts as a source of electric field and time-varying electric field acts as a source of magnetic field
  • d)
    time-varying magnetic field acts as a sink of electric field
Correct answer is option 'C'. Can you explain this answer?

Ameya Das answered

Maxwell's Equations:

Maxwell's equations are a set of four fundamental equations that describe how electric and magnetic fields interact. These equations are crucial in the study of electromagnetism and have many important implications.

Time-Varying Magnetic Field and Electric Field:

- According to Maxwell's equations, a time-varying magnetic field acts as a source of an electric field. This means that when a magnetic field changes with time, it creates an electric field in the surrounding space.
- Similarly, a time-varying electric field acts as a source of a magnetic field. This shows the interconnected nature of electric and magnetic fields and how they influence each other.

Implications of Time-Varying Fields:

- When a magnetic field undergoes changes over time, it induces an electric field. This phenomenon is known as electromagnetic induction and is the basis for many practical applications such as generators and transformers.
- The relationship between time-varying electric and magnetic fields is essential for understanding electromagnetic waves, which are propagating disturbances of electric and magnetic fields.

Conclusion:

In conclusion, Maxwell's equations reveal the intricate relationship between electric and magnetic fields, particularly when they vary with time. The concept that a time-varying magnetic field acts as a source of an electric field, and vice versa, is fundamental in the study of electromagnetism and has wide-ranging applications in various fields of science and technology.

Which of the following, is the longest wave ?       [1989]
  • a)
    X-rays
  • b)
    γ - rays
  • c)
    microwaves
  • d)
    radiowaves
Correct answer is option 'D'. Can you explain this answer?

Jatin Chakraborty answered
Rays  -    Wavelength
[Range in m]
X-rays    -  1 × 10–11 to 3 × 10–8
γ-rays     -  6 × 10–14 to 1 × 10–11
Microwaves    -  10–3 to 0.3
Radiowaves    -  10 to 104

The electric and magnetic field of an electromagneticwave are       [2007]
  • a)
    in opposite phase and perpendicular to eachother
  • b)
    in opposite phase and parallel to each other
  • c)
    in phase and perpendicular to each other
  • d)
    in phase and parallel to each other.
Correct answer is option 'C'. Can you explain this answer?

Sarthak Saini answered
Variation in magnetic field causes electric field and vice-versa.
In electromagnetic waves, .
Both  and    are in the same phase.
In electromagnetic waves
E = E0 sin(ωt - kx)
B = B0 sin(ωt - kx)
The electromagnetic waves travel in the
direction of 

Green-house effect is the heating up of earth's atmosphere due to         [2002]
  • a)
    green plants
  • b)
    infra-red rays
  • c)
    X-rays
  • d)
    ultraviolet rays
Correct answer is option 'B'. Can you explain this answer?

Aniket Chawla answered
Infrared rays is the cause of Green house effect. The glass transmits visible light and short infrared rays which are absorbed by plants. Then it emits long infrared rays, which are reflected back by glass.

Some scientists have predicted that a global nuclear war on the earth would be followed by a severe ‘nuclear winter’ with a devastating effect on life on earth. What might be the basis of this prediction?
  • a)
    Nuclear reactions absorb visible light causing dark days/nights
  • b)
    Nuclear reactions absorb atmospheric heat causing cooling
  • c)
    The clouds produced by global nuclear war would perhaps cover substantial parts of the sky preventing solar light from reaching many parts of the globe
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Nisha Patel answered
The use of nuclear weapons would cause the formation of smoke clouds preventing the light from the sun reaching earth surface and it will also deplete the atmosphere and therefore stopping the greenhouse effect and thus doubling the cooling effect.
Hence the correct answer is option C.

Chapter doubts & questions for Electromagnetic Waves - Physics Class 12 2025 is part of NEET exam preparation. The chapters have been prepared according to the NEET exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for NEET 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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