Chapter 19, Problem 49A

Interpretation Introduction

Interpretation: Though gamma rays are much more penetrating than alpha rays still the latter is more harmful, the reasons for it has to be explained. Also which ray is more ionizing has to be stated.

Concept introduction: Nuclear reactions are those where an unstable nuclide disintegrates in order to form a stable nuclide with emission of various radiations feasibly. It is called radioactivity of nucleus. The particles or rays emitted during the process are alpha, beta and gamma rays which cause a change in the identity of nucleus.

Beta particle is one that has unit negative charge and alpha particle is one that has 2 unit positive charges and is equivalent to helium atom ${}_2^4\text{He}$ .

Answer to Problem 49A

Though $\text{α}$ rays are least penetrating than $\text{γ}$ rays yet $\text{α}$ rays are most harmful to human body because of their ability to ionize cells and damage them.

Explanation of Solution

When radioactive substance disintegrates, three types of radiations are produced: $\text{α}$ , $\text{β}$ and $\text{γ}$ radiations. All three affect on the basis of their ability to penetrate into human body. Most penetrating is $\text{γ}$ ray and least is $\text{α}$ . $\text{α}$ rays can be obstructed by paper or metal foil simply because their speed is less due to its heavy mass of 4 units, equivalent to that of ${}_2^4\text{He}$ . $\text{β}$ rays can penetrates up to 1 cm into the human body.

Though $\text{α}$ rays are least penetrating than $\text{γ}$ rays yet $\text{α}$ rays are most harmful to human body because of their ability to ionize cells and hence damage them.

Conclusion

Though $\text{α}$ rays are least penetrating than $\text{γ}$ rays yet $\text{α}$ rays are most harmful to human body because of their ability to ionize cells and hence damage them.