Physics M.C.Q (1 Marks)

4. Infrared waves

Explanation:
Infrared waves can be used to take photographs during conditions of smoke, fog, etc. as these waves are scattered less than visible rays and hence travel longer distances through the atmosphere. So, using infrared waves can help Monica out.

4. More than 1

Explanation:
The ratio of frequencies of UV rays and IR rays in the glass is more than 1. This is because the frequency of UV rays is greater than that of infrared rays. This situation is applicable in glass or vacuum or air.

2. Power is transmitted in a direction perpendicular to both the field

Explanation:
For electromagnetic waves E and B are always perpendicular to each other and perpendicular to the direction of propagation. The direction of propagation is the direction of E × B.
The direction of propagation of the wave is the direction of propagation of its energy and power.

2. Giga hertz

4. Perpendicular to each other

Explanation:
The experimental set up of Thomson's experiment is shown in figure, 
According to this figure, the electric field is applied between two horizontal parallel plates, this field is directed in downward direction.
The cross in figure shows the magnetic field is directed inside the paper. Therefore, both the fields are perpendicular to each other.

3. 1

Explanation:
 Ratio = 1 because the speed of an electromagnetic wave in vacuum is independent of its wavelength or frequency. Therefore, the ratio of speed of infrared and ultraviolet rays in a vacuum is one.

1. Conduction current obeys Ohm's law whereas displacement current does not.

Explanation:
Displacement current is the current that occurs due to charging electric field  introduced by maxwell. It depends on the frequency of electric field while conduction current follows ohms law, requires medium displacement.Current doesnot follow ohms law nor require medium.

2. Gamma rays

Explanation:
Gamma rays have a maximum frequency.

1. Along the electric field.

Explanation:
As the electron is at rest initially, only the electric field will exert force on it. There will be no magnetic force on the electron in the stating. Hence, the electron will start moving along the electric field.

2. Ultraviolet Rays

Explanation:
Ultraviolet (UV) radiations in large quantities are highly harmful to humans. These rays in solar radiation on reaching earth are absorbed by the ozone layer in the atmosphere. UV rays are produced by special lamps such as mercury and from arc lamps and by very hot bodies like the sun.

2. Displacement current

4. In mutually perpendicular planes but vibrating in phase

Explanation:
The Electromagnetic wave consists of the two mutually perpendicular electric and magnetic fields present in the medium and also both being perpendicular to the direction of propagation of the wave. The two fields are in same phase as they obtain their peaks at the same instant.
An electromagnetic wave consists of periodically oscillating electric and the magnetic vector in mutually perpendicular planes but vibrating in phase.

2. Ultra-high frequency

Explanation:
UHF stands for Ultra high frequency. Cellular phones used radio waves to transmit voice communication in the Ultra high-frequency Band. The UHF band extends from 900 MHz to 5 x 109 Hz or 5000 MHz. Radio waves are produced by oscillating circuits having an inductor and capacitor.

2. Moving in a circular orbit.

4. falling in an electric field.

Solution:
Key concept:

1. An electromagnetic wave can be produced by accelerated or oscillating charge.
2. An oscillating charge is accelerating continuously, it will radiate electromagnetic waves continuously.
3. Electromagnetic waves are also produced when fast moving electrons are suddenly stopped by a metal target of high atomic number.

Here, in option (b) charge is moving in a circular orbit.
In circular motion, the direction of the motion of charge is changing continuously, thus it is an accelerated motion and this option is correct.
In option (d), the charge is falling in electric field. If a charged particle is moving in electric field it experiences a force or we can say it accelerates. We know an accelerating charge particle radiates electromagnetic waves. Hence option (d) is also correct.
Also, we know that a charge starts accelerating when it falls in an electric field.
Important points:

1. In an atom an electron is circulating around the nucleus in a stable orbit, although accelerating does not emit electromagnetic waves; it does so only when it jumps from a higher energy orbit to a lower energy orbit.
2. A simple LC oscillator and energy source can produce waves of desired frequency

1. polarization

3. Either ac or dc

4. both (A) and (B)

Explanation:
Maxwell's equation describe the fundamental laws of electricity and magnetism. His equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents.

2. Faraday's law and Ampere' law

Explanation:
Maxwell added the concept of displacement current in AMpere Circuit Law which governs the conduction in the wire of conduction current. After the deviation compass between capacitor Maxwell thought of magnetic lines which would be the result of varying current known as displacement current. So by continuing the displacement in Amperes law, Maxwell was able to show the result of Amperes conduction in circuit moving electrons and also the result of faraday generation of ME waves.

4. Infrared Waves

Explanation:
Infrared waves are heat radiations also known as heatwaves. These waves are produced by hot bodies and molecules. They do heating because water molecules present in most of the materials readily absorb infrared waves and their thermal motion increases, so they heat themselves and also heat their surroundings.

3. z - axis

Explanation:
Light wave is an electromagnetic wave in which E and B are at right angles to each other as well as at right angles to the direction of wave propagation. So from the given information in the question, the direction of B vector is in positive z direction.

D