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Radioactivity for NEET: 32 solved questions

Real NEET paper questions on radioactivity, part of nuclei. Each opens with the options, the correct answer and a step-by-step solution. Papers run from 1988 to 2021. No sign-in needed to read them.

What this topic asks

• Decay law and half-life — 17 questions
• Activity and decay constant — 10 questions
• Nature of alpha, beta and gamma radiation — 5 questions

All 32 questions with solutions

• The half-life of a radioactive nuclide is 100 h. The fraction of original activity that will remain after 150… NEET 2021
• The half-life of a radioactive sample undergoing α-decay is 1.4×10¹⁷ s. If the number of nuclei in the sample… NEET (Oct.) 2020
• The rate of radioactive disintegration at an instant for a radioactive sample of half life 2.2×10⁹ s is 10¹⁰… NEET (Odisha) 2019
• α-particle consists of NEET (National) 2019
• For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time ta… NEET 2018
• Radioactive material A has decay constant 8λ and material B has decay constant λ. Initially, they have same n… NEET 2017
• The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85%… NEET 2016
• A radio isotope X with a half life 1.4×10⁹ yr decays to Y which is stable. A sample of the rock from a cave w… CBSE AIPMT 2014
• The half-life of a radioactive isotope X is 20 yr. It decays to another element Y which is stable. The two el… NEET 2013
• A mixture consists of two radioactive materials A₁ and A₂ with half lives of 20 s and 10 s respectively. Init… CBSE AIPMT 2012
• The half-life of a radioactive isotope X is 50 yr. It decays to another element Y which is stable. The two el… CBSE AIPMT 2011
• The activity of a radioactive sample is measured as N₀ counts per minute at t=0 and (N₀)/e counts per minute… CBSE AIPMT 2010
• Two radioactive materials X₁ and X₂ have decay constants 5λ and λ respectively. If initially they have the sa… CBSE AIPMT 2008
• Two radioactive substances A and B have decay constants 5λ and λ respectively. At t=0 they have the same numb… CBSE AIPMT 2007
• In radioactive decay process, the negatively charged emitted β-particles are CBSE AIPMT 2007
• In a radioactive material the activity at time t₁ is R₁ and at a later time t₂, it is R₂. If the decay consta… CBSE AIPMT 2006
• The half-life of radium is about 1600 yr. Of 100 g of radium existing now, 25 g will remain unchanged after CBSE AIPMT 2004
• A sample of radioactive element has a mass of 10 g at an instant t=0. The approximate mass of this element in… CBSE AIPMT 2003
• A sample of radioactive elements contains 4×10¹⁰ active nuclei. If half-life of element is 10 days, then the… CBSE AIPMT 2002
• Half-life of a radioactive substance is 12.5 h and its mass is 256 g. After what time, the amount of remainin… CBSE AIPMT 2001
• Half-life period of a radioactive substance is 6 h. After 24 h activity is 0.01 μCi, what was the initial act… CBSE AIPMT 2001
• Which of the following is positively charged? CBSE AIPMT 2001
• The half-life of a radioactive material is 3 h. If the initial amount is 300 g, then after 18 h, it will rema… CBSE AIPMT 2000
• The relationship between disintegration constant (λ) and half-life (T) will be CBSE AIPMT 2000
• Alpha particles are CBSE AIPMT 1999
• Half-lives of two radioactive substances A and B are respectively 20 min and 40 min. Initially, the samples o… CBSE AIPMT 1998
• The activity of a radioactive sample is measured as 9750 counts/min at t=0 and as 975 counts/min at t=5 min.… CBSE AIPMT 1997
• The most penetrating radiation out of the following is CBSE AIPMT 1997
• The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life 30 min dec… CBSE AIPMT 1995
• The half-life of radium is 1600 yr. The fraction of a sample of radium that would remain after 6400 yr is CBSE AIPMT 1991
• A radioactive element has half-life period 800 yr. After 6400 yr, what amount will remain ? CBSE AIPMT 1989
• A radioactive sample with a half-life of 1 month has the label : 'Activity = 2 microcurie on 1-8-1991'. What… CBSE AIPMT 1988