JEE Main 2021 (Online) 26th February Evening Shift | Atoms and Nuclei Question 198 | Physics

A radioactive sample is undergoing $$\alpha$$ decay. At any time t₁, its activity is A and another time t₂, the activity is $${A \over 5}$$. What is the average life time for the sample?

$${{\ln 5} \over {{t_2} - {t_1}}}$$

$${{\ln ({t_2} + {t_1})} \over 2}$$

$${{{t_1} - {t_2}} \over {\ln 5}}$$

$${{{t_2} - {t_1}} \over {\ln 5}}$$

JEE Main 2021 (Online) 26th February Morning Shift

MCQ (Single Correct Answer)

-1

If $$\lambda$$₁ and $$\lambda$$₂ are the wavelengths of the third member of Lyman and first member of the Paschen series respectively, then the value of $$\lambda$$₁ : $$\lambda$$₂ is :

7 : 135

7 : 108

1 : 9

1 : 3

JEE Main 2021 (Online) 25th February Evening Shift

MCQ (Single Correct Answer)

-1

The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n = 2 to n = 1 state is :

194.8 nm

490.7 nm

913.3 nm

121.8 nm

JEE Main 2021 (Online) 25th February Morning Shift

MCQ (Single Correct Answer)

-1

Out of Syllabus

Two radioactive substances X and Y originally have N₁ and N₂ nuclei respectively. Half life of X is half of the half life of Y. After three half lives of Y, number of nuclei of both are equal. The ratio $${{{N_1}} \over {{N_2}}}$$ will be equal to :

$${1 \over 8}$$

$${3 \over 1}$$

$${1 \over 3}$$

$${8 \over 1}$$

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