Modern Physics

1.Which one of the following is essential in the construction of a nuclear reactor?
 
A. Cobalt
 
B. Nickel
 
C. Zirconium
 
D. Tungsten
 
Option”C” is correct

Zirconium elements is essential for construction in nuclear reactors.

Zirconium is a chemical element with symbol Zr and atomic number 40. The name zirconium is taken from the name of the mineral zircon, the most important source of zirconium. The word zircon comes from the Persian word zargun زرگون, meaning “gold-colored”. A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a self-sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships.

2.The alpha particle has two units of positive charge, its mass is approximately equal to
 
A. two protons
 
B. an atom of helium
 
C. sum of masses of two positrons and two neutrons
 
D. two positrons as each positron carries a single positive charge
 
Option”B” is correct

The α−particle carries two positive charges. Its mass is very nearly equal to that of an atom of helium.

Positively charged particle emitted by various radioactive materials during decay. It consists of two neutrons and two protons, and is thus identical to the nucleus of a helium atom. The rest mass of the alpha particle amounts to 6.64424. 10-27 kg, or 3.7273.

A helium atom is an atom of the chemical element helium. Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with either one or two neutrons, depending on the isotope, held together by the strong force.

3.Cobalt-60 is commonly used in radiation therapy because it emits-
 
A. Alpha rays
 
B. Beta rays
 
C. Gamma rays
 
D. X-rays
 
Option”C” is correct
Cobalt-60 emits two high energy gamma rays, making cobalt-60 both an internal and external hazard. The primary exposure pathways of concern are ingestion (drinking water and fish consumption), and exposure by inhalation and external exposure.
4.Which of the following is used as a Newton controller in a nuclear reactor?
 
A. Heavy water
 
B. Graphite
 
C. Cadmium or Boron
 
D. Aluminium
 
Option”C” is correct
Cadmium rods are used as control rods as they are capable of absorbing neutrons without themselves fissioning.
5.An atomic pile is used for
 
A. Producing X-rays
 
B. Conducting nuclear fission
 
C. Conducting thermonuclear fusion
 
D. accelerating atoms
 
Option”C” is correct

The correct answer is Conducting nuclear fission.

  • The anatomic pile is used for Conducting nuclear fission.

Key Points

  • Nuclear Fission:
    • The nuclear reaction in which a heavy nucleus splits into two nuclei of nearly equal mass is called nuclear fission.
    • Chain Reaction:
      • When uranium atom is bombarded with slow neutrons, fission takes place. With the fission of each uranium nucleus, on an average, three neutrons and large energy are released. These neutrons cause further fission. Clearly, a chain of fission of uranium nucleus starts which continues till the whole of uranium is exhausted. This is called a chain reaction.
  • A nuclear reactor is an arrangement in which controlled nuclear fission reaction takes place.
  • The atom bomb is based on nuclear fission.

6.Curie is the name of whose unit
 
A. Radioactivity
 
B. Temperature
 
C. Heat
 
D. Energy
 
Option”A” is correct
A material’s radioactivity is measured in becquerels (Bq, international unit) and curies (Ci, U.S. unit). Because a curie is a large unit, radioactivity results are usually shown in picocuries (pCi). A picocurie is one trillionth of a curie. The higher the number, the more radiation released by the material.
7.Energy is generated in a nuclear reactor
 
A. By controlled fusion fusion
 
B. By uncontrolled fusion
 
C. By controlled fission
 
D. By uncontrolled fragmentation
 
Option”C” is correct.
Nuclear reactors are the heart of a nuclear power plant. They contain and control nuclear chain reactions that produce heat through a physical process called fission.
8.Why is nuclear fusion also called thermonuclear reaction?
 
A. Fusion converts nuclear energy into heat
 
B. Fusion requires extremely high temperature conditions
 
C. Fusion produces a lot of heat
 
D. Fusion reaction takes place in sunlight
 
Option”B” is correct
Thermonuclear fusion is a way to achieve nuclear fusion by using extremely high temperatures. So basically we can say nuclear fusion at high temperature will be thermo-nuclear reaction. Temperature is a measure of the average kinetic energy of particles, so by heating the material it will gain energy. After reaching sufficient temperature, given by the Lawson criterion, the energy of accidental collisions within the plasma is high enough to overcome the Coulomb barrier and the particles may fuse together.
9.Carbon dating is used to determine the age of fossils. It is estimated by
 
A. The planets
 
B. Fossils
 
C. Babies
 
D. Rocks
 
Option”B” is correct.
Fossils are the preserved remains, traces or impressions of organisms or their parts that lived in a past geological age. These could include the whole body of the extinct organism, inorganic remains of plants and animals, remains of bones or even moulds, casts and footprints embedded in stratified rocks.
To find out the approximate age of the fossils, a carbon dating method is commonly used. This is based on the principle of radioactive decay.
10.Gamma rays are
 
A. Electromagnetic waves
 
B. Helium nucleus
 
C. Fast moving electron
 
D. Single ionized gas atom
 
Option”A” is correct
Gamma rays are a type of electromagnetic radiation that results from a redistribution of electric charge within a nucleus. Gamma rays are essentially very energetic X rays ; the distinction between the two is not based on their intrinsic nature but rather on their origins.