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mediumMCQTNPSC Group 2 Official Paper (2016)General Studies, Aptitude and Mental Ability Test
1.5 marks

Arrange the following in the increasing order of their penetration powers

Ⅰ. Alpha rays

Ⅱ. Beta particles

Ⅲ. Gamma rays

  1. A
    Ⅰ - Ⅱ - Ⅲ
  2. B
    Ⅱ - Ⅰ - Ⅲ
  3. C
    Ⅱ - Ⅲ - Ⅰ
  4. D
    Ⅲ - Ⅱ - Ⅰ

Solution & Step-by-step Explanation

Penetration Power of Radiation Types

Understanding the penetration power of different types of radiation is crucial in physics, especially when studying radioactivity and nuclear processes. Radiation interacts with matter in various ways, determining how far it can travel through a substance before being absorbed or stopped. We will arrange alpha rays, beta particles, and gamma rays in the increasing order of their penetration powers.

Understanding Different Radiation Types

Let's first define each type of radiation mentioned, which are commonly encountered in discussions about nuclear decay and radiation safety:

- Alpha Rays (Ⅰ): These are positively charged particles consisting of two protons and two neutrons, identical to a helium nucleus (). They are relatively heavy and carry a strong positive charge.
- Beta Particles (Ⅱ): These are high-energy electrons or positrons. They are much lighter than alpha particles and carry a negative (electron, ) or positive (positron, ) charge.
- Gamma Rays (Ⅲ): These are a form of electromagnetic radiation, specifically high-energy photons. Unlike alpha and beta particles, gamma rays have no mass and no charge.

Penetration Power Analysis

The ability of radiation to penetrate matter depends primarily on its mass, charge, and energy. Particles with larger mass and charge tend to interact more frequently with the electrons and nuclei of the material they pass through, causing them to lose energy more rapidly and thus have lower penetration power. Electromagnetic waves like gamma rays, having no mass or charge, interact much less frequently.
Radiation TypeCharacteristicsInteraction with MatterPenetration PowerTypical Shielding
Alpha Rays (Ⅰ)Heavy, positively charged ( nucleus).Strong ionization due to large mass and charge; many collisions with atomic electrons.Lowest – They lose energy quickly and travel only a short distance.A sheet of paper, the outer layer of skin, or a few centimeters of air.
Beta Particles (Ⅱ)Light, negatively or positively charged (electrons/positrons).Less intense ionization than alpha particles; fewer collisions due to smaller mass and charge.Medium – They can travel further than alpha particles but are still easily stopped.A few millimeters of aluminum or a few meters of air.
Gamma Rays (Ⅲ)No mass, no charge (high-energy photons).Interactions are less frequent and involve processes like photoelectric effect, Compton scattering, and pair production.Highest – Being massless and chargeless, they interact very weakly with matter, making them extremely penetrating.Thick lead, concrete, or several meters of water are needed for effective shielding.
Arranging by Increasing Penetration

Based on the analysis of their characteristics and how they interact with matter, the increasing order of their penetration powers is:

1. Alpha Rays (Ⅰ): They are the least penetrating type of radiation.
2. Beta Particles (Ⅱ): They have moderate penetration power, greater than alpha rays but less than gamma rays.
3. Gamma Rays (Ⅲ): They are the most penetrating type of radiation.

Therefore, the correct arrangement in the increasing order of their penetration powers is Ⅰ - Ⅱ - Ⅲ.

Practice this question

Try it yourself before checking the explanation above.

Arrange the following in the increasing order of their penetration powers

Ⅰ. Alpha rays

Ⅱ. Beta particles

Ⅲ. Gamma rays
A
Ⅰ - Ⅱ - Ⅲ
B
Ⅱ - Ⅰ - Ⅲ
C
Ⅱ - Ⅲ - Ⅰ
D
Ⅲ - Ⅱ - Ⅰ

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