Part – B (General Studies) (English) NDA/NA SOLVED PAPER 2017 (II) (101 to 150)

Total Questions: 50

41. In a vacuum, a five-rupee coin, a feather of sparrow bird and a mango are dropped simultaneously from the same height. The time taken by them to reach the bottom is t₁, t₂ and t₃ respectively. In this situation, we will observe that:

Correct Answer: (d) t₁ = t₂ = t₃
Solution:

In vacuum there is no air resistance, so all bodies in free fall have the same acceleration g regardless of mass or shape.

Starting from the same height with zero initial velocity, they all take the same time to reach the ground, so t₁ = t₂ = t₃

42. Electron emission from a metallic surface by application of light is known as:

Correct Answer: (b) Photo electric emission
Solution:

Emission of electrons from a metal surface when light (electromagnetic radiation) falls on it is the photoelectric effect, also called photoelectric emission.​

Thermionic emission is due to heating, high‑field and auto‑electronic emission occur under very strong electric fields, not by light.​

43. How long does light take to reach the Earth from the Sun?

Correct Answer: (b) About 8 minutes
Solution:Sunlight takes about 8 minutes 20 seconds to travel from the Sun to Earth, usually rounded to about 8 minutes.

44. Radioactivity is measured by:

Correct Answer: (a) GM Counter
Solution:

Radioactivity (ionizing radiation from radioactive substances) is commonly measured with a Geiger–Müller (GM) counter.​

Polarimeters, calorimeters and colorimeters are used for optical rotation, heat, and colour intensity measurements respectively, not radioactivity

45. The mirrors used as rear-view mirrors in vehicles are:

Correct Answer: (b) convex
Solution:

  • Rear‑view mirrors in vehicles use convex mirrors because they provide a wider field of view, letting the driver see more area behind with one mirror.​

  • Concave mirrors magnify and have a narrow field; plane mirrors show only a limited region; cylindrical are not used for standard rear view.​

46. Which one of the following waves is used for detecting forgery in currency notes?

Correct Answer: (a) Ultraviolet waves
Solution:

  • Currency notes often have fluorescent security features that glow under ultraviolet (UV) light), helping detect forgeries.​

  • Infrared, radio and microwaves are not typically used for checking note authenticity.​

47. The majority charge carriers in a p-type semiconductor are:

Correct Answer: (d) holes
Solution:

  • A p‑type semiconductor has acceptor impurities; its majority charge carriers are holes (absence of electrons).​

  • Free/conduction electrons are minority carriers in p‑type; ions are fixed in the lattice and do not move as current carriers.

48. The ionisation energy of hydrogen atom in the ground state is:

Correct Answer: (b) 13.6 eV
Solution:

Ionisation energy of hydrogen in ground state is 13.6 eV, the energy needed to remove the electron completely from n=1.​

  • 13.6 MeV or 13.6 J are many orders of magnitude too large; zero would mean the electron is unbound, which is false.

49. When pure water boils vigorously, the bubbles that rise to the surface are composed primarily of:

Correct Answer: (d) water vapour
Solution:

At vigorous boiling, bubbles consist almost entirely of water vapour, Initially some dissolved air may escape, but once fully boiling, decomposition to hydrogen or oxygen does not occur, so options (b) and (c) are wrong

50. Which compound, when dissolved in water, conducts electricity and forms a basic solution?

Correct Answer: (d) NaOH
Solution:

NaOH (sodium hydroxide) is an ionic compound; in water it dissociates into ions and conducts electricity, and the solution is basic.​

HCl and CH₃COOH give acidic solutions; CH₃OH is a covalent alcohol that is a non‑electrolyte in dilute solution.