IN JEE ADV 2015 PAPER (1) (PHY) I HAVE A DOUBT.IN MATCHING IT AS GIVEN GAMMA EMISSION IN COLOUM (I) AND ACCORDING TO OFFICIAL KEY IT IS NOT MATCHED ITH THE OPTION CONTAINING Co(60,27) IN COLOUM(II) WHY???

Let's delve into your question regarding the JEE Advanced 2015 Physics paper, specifically the gamma emission and its relation to Co-60. It seems like there might be some confusion about the gamma emission process and how it relates to the options provided in the exam. Understanding the nature of gamma emissions and the characteristics of cobalt-60 will clarify why the official answer key does not match your expectations.

Understanding Gamma Emission

Gamma emission is a type of radioactive decay where an unstable nucleus releases energy in the form of gamma rays. This process typically occurs after other forms of decay, such as alpha or beta decay, when the nucleus is left in an excited state. The emission of gamma rays helps the nucleus reach a more stable state.

Cobalt-60: A Case Study

Cobalt-60 (Co-60) is a well-known radioactive isotope that undergoes beta decay. In this process, a neutron in the nucleus is converted into a proton, emitting a beta particle (an electron) and an antineutrino. The resulting nucleus is nickel-60 (Ni-60), which is in an excited state. To reach a stable configuration, Ni-60 then emits gamma radiation.

• Decay Process: Co-60 → Ni-60 + β- + ν (beta decay)
• Gamma Emission: Ni-60 (excited) → Ni-60 + γ (gamma emission)

Why the Confusion?

In the context of your question, the key point is that while Co-60 does indeed emit gamma rays, it does so after undergoing beta decay. If the question in the JEE paper was specifically asking about gamma emission directly from Co-60 without mentioning the intermediate beta decay, it might have led to the confusion. The official answer key likely reflects the understanding that Co-60 does not emit gamma rays directly; rather, it is the product of its decay (Ni-60) that does.

Clarifying the Options

When matching options in the exam, it’s crucial to consider the entire decay process. If the question was structured to ask about gamma emission specifically from Co-60, then the answer would indeed not match with the option containing Co-60 in Column II, as it does not emit gamma rays directly. Instead, it is the decay product that is responsible for gamma emission.

Key Takeaway

In summary, the reason the official key does not match the option containing Co-60 is that the gamma emission is not a direct result of Co-60 itself but rather a consequence of its decay to Ni-60. Understanding the sequence of decay processes is essential in nuclear physics, especially in questions involving radioactive isotopes.

If you have any further questions or need clarification on specific points, feel free to ask!