Electromagnetic Waves

Step 1: Understanding the Concept:
The question asks to classify X-rays from the given options. This requires knowledge of the nature of X-rays and the electromagnetic spectrum.
Step 2: Detailed Explanation:
X-rays are a form of high-energy radiation. They are not particles with mass and charge like electrons or ions.
- A moving electron is a stream of negatively charged fundamental particles (beta radiation).
- A moving positive or negative ion is a charged atom or molecule.
- Electromagnetic waves are disturbances in the electromagnetic field that propagate through space, carrying energy. They do not have mass or charge. The electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
X-rays are produced when high-energy charged particles (like electrons) rapidly decelerate, typically by hitting a metal target. The kinetic energy of the particles is converted into electromagnetic radiation. X-rays fall between ultraviolet light and gamma rays in the electromagnetic spectrum, characterized by their short wavelength and high frequency/energy.
Step 3: Final Answer:
X-rays are a form of electromagnetic radiation, i.e., electromagnetic waves. Option (D) is correct.

Step 1: Understanding the Concept:
An electromagnetic (EM) wave consists of oscillating electric field ( ) and magnetic field ( ) vectors. These fields are perpendicular to each other and also perpendicular to the direction of wave propagation. A key characteristic of EM waves is the relationship between the phases of these two fields.
Step 2: Detailed Explanation:
According to Maxwell's equations for EM waves in a vacuum or free space, the electric and magnetic fields are always in phase. This means that they reach their maximum values at the same time and at the same point in space. Similarly, they both pass through zero and reach their minimum values simultaneously.
If the electric field is described by , the magnetic field will be described by .
The phase for both waves is the term . Since the phase term is identical for both, the phase difference between them is zero.
Step 3: Final Answer:
The electric and magnetic fields in an electromagnetic wave oscillate in phase with each other. Therefore, the phase difference between them is zero. Option (D) is correct.

Step 1: Electromagnetic waves are produced by the acceleration of electric charges. When charges accelerate, they create time-varying electric and magnetic fields that are mutually perpendicular and propagate through space.
Step 2: These varying electric and magnetic fields sustain each other as they move through space. The changing electric field generates a magnetic field, and the changing magnetic field induces an electric field, allowing the wave to propagate even in vacuum without the need for any medium.
Step 3: The speed of electromagnetic waves (speed of light) in vacuum is derived from Maxwell’s equations and is given by: where is the permeability of free space, and is the permittivity of free space.
Hence, the velocity of electromagnetic waves depends solely on these two fundamental constants and , highlighting the intrinsic properties of free space.

Step 1: Understanding TV transmission frequencies.
TV transmission utilizes electromagnetic waves in the radio frequency spectrum. The typical range for TV broadcast is between 30 MHz to 300 MHz. This range is commonly used for UHF and VHF channels in analog and digital TV transmission.
Step 2: Explanation of frequency ranges.
- (A) 30 - 300 Hz: This is a very low frequency range, used for signals such as audio frequencies, not for TV.
- (B) 30 - 300 kHz: This range is used for AM radio transmission, not for TV.
- (C) 30 - 300 MHz: This is the correct frequency range for TV transmission (UHF and VHF).
- (D) 30 - 300 GHz: This range is far higher than what is used for TV broadcasting, typically used for microwave transmission.
Step 3: Conclusion.
The correct frequency range for TV transmission is 30 - 300 MHz.

Step 1: Understanding X-rays.
X-rays are a form of electromagnetic radiation, much like light, but with much shorter wavelengths. They are produced when high-energy electrons collide with matter, releasing energy in the form of electromagnetic waves.
Step 2: Explanation of each option.
- (A) moving electron: Incorrect. X-rays are not composed of moving electrons; rather, they are electromagnetic waves produced by the interaction of electrons with matter.
- (B) moving positive ions: Incorrect. X-rays are not made of ions but rather electromagnetic radiation.
- (C) moving negative ion: Incorrect. Similar to option (B), X-rays are not generated by ions but by electromagnetic radiation.
- (D) electromagnetic waves: Correct. X-rays are a type of electromagnetic wave, just like visible light, radio waves, and gamma rays.
Step 3: Conclusion.
X-rays are electromagnetic waves.

Step 1: Understanding electromagnetic waves.
Electromagnetic waves include visible light, radio waves, X-rays, gamma rays, and infrared rays. They all travel at the speed of light in a vacuum and can propagate through a vacuum.
Step 2: Elimination of options.
- (A) Alpha rays: Alpha rays are not electromagnetic waves. They are a form of particle radiation consisting of helium nuclei.
- (B) Gamma rays: Gamma rays are electromagnetic waves with high energy.
- (C) Infrared rays: Infrared rays are electromagnetic waves that are used for heat and communication.
- (D) X-rays: X-rays are also electromagnetic waves.
Conclusion: Alpha rays are not an electromagnetic wave.

Step 1: Speed of electromagnetic waves.
The speed of an electromagnetic wave in a material medium is given by the formula: where is the speed of light in a vacuum, is the relative permittivity, and is the relative permeability of the medium. The wave’s speed depends on the medium’s properties, not its frequency, wavelength, or intensity.
Step 2: Elimination of options.
- (A) Upon its wavelength: The speed of light is related to its wavelength and frequency through the equation . Wavelength is inversely proportional to frequency in a given medium.
- (B) Upon its frequency: The frequency of an electromagnetic wave is related to its speed in a particular medium.
- (C) Upon its intensity: The intensity of the wave does not affect the speed of light in the medium. Intensity is related to the amplitude of the wave, not its velocity.
- (D) Upon its permittivity: The speed of light depends on the permittivity of the medium.
Conclusion: The speed of the electromagnetic wave does not depend on its intensity.