Chapter 24, Problem 91A

Interpretation Introduction

Interpretation:

Effect of alpha radiation inside and outside a human body is to be described.

Concept introduction:

In a nuclear reaction, unstable nuclide disintegrates into stable nuclide with emission of various radiations spontaneously. It is called radioactivity of nucleus. Emission of rays like alpha, beta and gamma rays occur in the process which changes the identity of nucleus.

During a nuclear change, an element undergoes change in its atomic mass or atomic number or both by emission of charged particles such as beta particle, alpha particle. 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 ${}_2^4\text{He}$. Emission of proton, beta particle, alpha particle causes a change in atomic number of element.

Answer to Problem 91A

Due to heavy mass, alpha rays cannot penetrate into layer of dead layer of human skin and can be blocked easily by a paper sheet. So they are not a threat if outside the body. But alpha radiations have ability to multiply ionize and hence damage the cells if radioactive decay occurs from an atom inside the body. It can also damage the cornea of eyes.

Explanation of Solution

An alpha particle is one that has 2 unit positive charges and is equivalent to helium atom ${}_2^4\text{He}$. These particles make up alpha radiations which are slow in movement as compared to beta and gamma rays because of 4 units mass and 2 units charge on it.

Because of 2 unit of charge on alpha particle they are highly ionizing and comparatively slow due to 4 unit mass(that is heavy mass) than gamma and beta rays. Due to heavy mass, it cannot penetrate into layer of dead layer of human skin and can be blocked easily by a paper sheet. So they are not a threat if outside the body.

But alpha radiations have ability to multiply ionize and hence damage the cells if radioactive decay occurs from an atom inside the body. It can also damage the cornea of eyes.

Conclusion

Due to heavy mass, alpha rays cannot penetrate into layer of dead layer of human skin and can be blocked easily by a paper sheet. So they are not a threat if outside the body. But alpha radiations have ability to multiply ionize and hence damage the cells if radioactive decay occurs from an atom inside the body. It can also damage the cornea of eyes.