General Knowledge (Part-B: English) NDA/NA SOLVED PAPER 2021-II (51 to 100)

Total Questions: 50

11. What is the maximum number of electrons in the M-Shell?

Correct Answer: (c) 18
Solution:Bohr and Bury gave the following rules for the distribution of electrons around the nucleus.
  • Electrons are revolving around the nucleus in different orbits or shells. These energy shells are represented by numbers 1,2, 3, 4 or K, L, M, N.
  • The maximum number of electrons in any shell cannot exceed 2n2, where n is the number of that energy level.
  • The maximum number of electrons that can be accommodated in the outermost orbit is 8. The next to the outermost shell (penultimate shell) can have at the most 18 electrons.

12. Chlorine occurs in nature in two isotopic forms of masses 35 u and 37 u in the ratio of 3: 1 respectively. What is the average atomic mass of the Chlorine atom?

Correct Answer: (b) 35.5 u
Solution:

13. Which one of the following element's isotopes is used in the treatment of cancer?

Correct Answer: (c) Cobalt
Solution:Cobalt is a radioactive element that emits gamma rays. A radioactive element has excess energy which is emitted from the nucleus as gamma radiation and the Isotopes of any element has some number of protons but a different number of neutrons in each atom. In the treatment of cancer cobalt therapy or cobalt-60 therapy is the medical use of gamma rays from the radioisotope cobalt-60.

14. To protect steel and iron from rusting, a thin layer of which one of the following metals is applied?

Correct Answer: (b) Zinc
Solution:Zinc is used to protect the iron from corrosion because it is more electropositive than iron. Galvanising is a method of rust prevention. The iron or steel object is coated in a thin layer of zinc.
This stops oxygen and water from reaching the metal underneath. Zinc is more electropositive than iron, hence it is more reactive than iron, so it oxidizes in preference to the iron object.

15. Cinnabar is an ore of which one of the following?

Correct Answer: (c) Mercury
Solution:The cinnabar is a mercury sulfide mineral and is the primary source of mercury. Mercury is a naturally occurring metallic element and is often found in air, water, and soil in variable amounts.
Exposure to mercury, even in small amounts, may cause serious health problems and is a threat to the normal development of children.

16. Imagine a current-carrying straight conductor with magnetic field of lines in anti-clockwise direction. Then the direction of current is determined by

Correct Answer: (c) the Right-Hand Thumb rule and it would be in the upward direction
Solution:It is given that the magnetic field associated with a current-carrying straight conductor is in an anticlockwise direction. Further, the conductor was held along the east-west direction. Therefore, according to the right-hand thumb rule, the direction of current through it will be in the upward direction.

17. The device used to produce electric current is known as

Correct Answer: (b) generator
Solution:An electric generator is a device that converts mechanical energy obtained from an external source into electrical energy as the output. The modern-day generator works on the principle of electromagnetic induction discovered by Michael Faraday in 1831-32. Faraday discovered that the above flow of electric charges could be induced by moving an electrical conductor, such as a wire that contains electric charges, in a magnetic field.
This movement creates a voltage difference between the two ends of the wire or electrical conductor, which in turn causes the electric charges to flow, thus generating electric current.

18. Myopia is a defect in human vision where an image of a

Correct Answer: (c) distant object is focused before the retina.
Solution:Due to myopia the eyes can see nearby objects clearly but cannot see distant objects. This defect is caused due to the formation of the image of a distant object in front of the retina.
An eye suffers from the defect of myopia due to the following two reasons
1. Abnormally long eyeball
2. Abnormally high convexity of the eye lens
This defect is corrected by using spectacles having suitable concave lenses. The concave lenses diverge the light rays, so the image is formed exactly on the retina.

19. Tyndall effect is a phenomenon of

Correct Answer: (a) scattering of light by the colloidal particles.
Solution:The Tyndall effect, also known as Tyndall scattering, is light scattering by particles in a colloid or a very fine suspension. Under the Tyndall effect, the longer wavelengths are more transmitted while the shorter wavelengths are more diffusely reflected via scattering.
The Tyndall effect is seen when light-scattering particulate matter is dispersed in an otherwise light-transmitting medium, when the diameter of an individual particle is the range of roughly between 40 and 900 nm, i.e. somewhat below or near the wavelengths of visible light (400-750 nm).

20. Twinkling of stars is primarily due to the atmospheric

Correct Answer: (a) refraction
Solution:The twinkling of a star is due to the atmospheric refraction of starlight. The starlight, on entering the earth's 7 atmosphere, undergoes refraction continuously before it reaches the earth.
Since the stars are very distant, they approximate point-sized sources of light. As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering eye flickers the star sometimes appears brighter and sometimes fainter, which is the twinkling effect.