JEE Main 2020 (Online) 6th September Evening Slot | Atoms and Nuclei Question 110 | Physics

JEE Main 2020 (Online) 6th September Evening Slot

MCQ (Single Correct Answer)

-1

Given the masses of various atomic particles
m_p = 1.0072 u, m_n = 1.0087 u, m_e = 0.000548 u,
$${m_{\overline v }}$$ = 0, m_d = 2.0141 u, where p $$ \equiv $$ proton, n $$ \equiv $$ neutron,
e $$ \equiv $$ electron, $$\overline v $$ $$ \equiv $$ antineutrino and d $$ \equiv $$ deuteron. Which of the following process is allowed by momentum and energy conservation?

n + n $$ \to $$ deuterium atom
(electron bound to the nucleus)

n + p $$ \to $$ d + $$\gamma $$

p $$ \to $$ n + e⁺ + $$\overline v $$

e⁺ + e^- $$ \to $$ $$\gamma $$

JEE Main 2020 (Online) 5th September Evening Slot

MCQ (Single Correct Answer)

-1

A radioactive nucleus decays by two different processes. The half life for the first process is 10 s and that for the second is 100 s. The effective half life of the nucleus is close to :

12 sec

9 sec

55 sec

6 sec

JEE Main 2020 (Online) 5th September Morning Slot

MCQ (Single Correct Answer)

-1

Activities of three radioactive substances A, B and C are represented by the curves A, B and C, in the figure. Then their half-lives
$${T_{{1 \over 2}}}\left( A \right)$$ : $${T_{{1 \over 2}}}\left( B \right)$$ : $${T_{{1 \over 2}}}\left( C \right)$$ are in the ratio : JEE Main 2020 (Online) 5th September Morning Slot Physics - Atoms and Nuclei Question 112 English

JEE Main 2020 (Online) 5th September Morning Slot Physics - Atoms and Nuclei Question 112 English

3 : 2 : 1

2 : 1 : 1

4 : 3 : 1

2 : 1 : 3

JEE Main 2020 (Online) 3rd September Evening Slot

MCQ (Single Correct Answer)

-1

The radius R of a nucleus of mass number A can be estimated by the formula
R = (1.3 $$ \times $$ 10^–15)A^1/3 m.
It follows that the mass density of a nucleus is of the order of :

(M_prot. $$ \cong $$ M_neut $$ \simeq $$ 1.67 $$ \times $$ 10^–27 kg)

10²⁴ kg m^–3

10¹⁰ kg m^–3

10¹⁷ kg m^–3

10³ kg m^–3

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