Correct Option
(c) Cobalt-60 is a radioactive isotope extensively utilized in radiation therapy, primarily for the treatment of various cancers. While it undergoes beta decay, its therapeutic efficacy is attributed to the emission of high-energy gamma rays. These gamma rays possess significant penetrating power, enabling them to target and destroy cancerous cells located deep within tissues, while minimizing damage to surrounding healthy cells. The predictable decay characteristics and potent gamma ray emission of Cobalt-60 make it a standard source for external beam radiotherapy.
Incorrect Options
(a) Alpha rays consist of heavy, positively charged particles (helium nuclei). Due to their large mass and charge, they have very low penetrating power and are readily absorbed by superficial layers of tissue. Consequently, they are unsuitable for treating deep-seated tumors in radiation therapy.
(b) Cobalt-60 does emit beta rays during its radioactive decay. However, beta rays have a limited range and penetration depth in biological tissues. They are typically employed for localized or superficial radiation treatments, rather than for the deep tissue therapies for which Cobalt-60 is primarily known due to its gamma ray emission.
(d) X-rays are a form of electromagnetic radiation produced artificially when high-speed electrons strike a metal target. They originate from electron transitions outside the nucleus. In contrast, gamma rays are emitted from the nucleus of an atom during radioactive decay. Cobalt-60 emits gamma rays, not X-rays, as a product of its nuclear transformation.