Question 32: EM waves

Question

ext { Match the LIST-I with LIST-II }

List-I
List-II

A.
Radio-wave
I.
is produced by Magnetron valve

B.
Micro-wave
II.
due to change in the vibrational modes of atoms

C.
Infrared-wave
III.
due to inner shell electrons moving from higher energy level to lower energy level

D.
X-ray
IV.
due to rapid acceleration of electrons

Choose the correct answer from the options given below:

Accepted Answer

Radio-waves
1. Radio waves have the longest wavelengths in the EM spectrum. They are artificially generated by transmitters. The core process involves an oscillating electric current in a special conductor called an antenna.
2. According to electromagnetic theory, an accelerating electric charge produces electromagnetic waves. In an antenna, electrons are rapidly accelerated back and forth.
3. So, the radio waves are produced due to rapid acceleration of electrons.
Micro-waves
1. Micro-waves are high-frequency radio waves. While they can be produced by acceleration, high-power microwaves (like those in radar or microwave ovens) are generated using special vacuum tubes.
2. The most common device for this is the Magnetron (or Klystron). A Magnetron uses a magnetic field to control the flow of electrons in a vacuum, causing them to oscillate at microwave frequencies.
3. Hence the Micro-wave is produced by Magnetron valve.
Infrared-waves
1. Infrared waves are often perceived as heat. All objects above absolute zero emit infrared radiation.
2. This emission arises from the thermal motion of atoms and molecules. When the atoms in a molecule vibrate or rotate, they change energy states. The transition between these vibrational and rotational energy levels results in the emission of infrared photons.
3. Hence, the infrared waves are produced due to change in the vibrational modes of atoms.
X-rays
1. X-rays have very high energy and short wavelengths. They are typically produced in X-ray tubes.
2. There are two main ways X-rays are produced:
(A) Braking Radiation: When high-speed electrons are suddenly stopped by a metal target.
(B) Characteristic X-rays: When a high-energy electron knocks an electron out of an inner shell (like the K-shell) of an atom, a vacancy is created. An electron from a higher energy outer shell falls into this vacancy. The large energy difference is released as an X-ray photon.
3. Hence, it is due to inner shell electrons moving from higher energy level to lower energy level.
So,
A (Radio-wave) Ã¢ÂÂ IV
B (Micro-wave) Ã¢ÂÂ I
C (Infrared-wave) Ã¢ÂÂ II
D (X-ray) Ã¢ÂÂ III
Hence, the correct option is (C).

Answer

A-IV, B-II, C-I, D-III

Answer

A-IV, B-III, C-I, D-II

Answer

A-IV, B-I, C-II, D-III

Answer

A-II, B-IV, C-III, D-I

EM waves

Choose the correct answer: