JEE Main 2017 (Online) 8th April Morning Slot | Atoms and Nuclei Question 204 | Physics

According to Bohr’s theory, the time averaged magnetic field at the centre (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the n^th orbit is proportional to : (n = principal quantum number)

$${n^{ - 4}}$$

$${n^{ - 5}}$$

n^$$-$$3

n^$$-$$2

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MCQ (Single Correct Answer)

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Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths r = $${{\lambda _1}}$$/$${{\lambda _2}}$$, is given by:

JEE Main 2017 (Offline) Physics - Atoms and Nuclei Question 205 English

JEE Main 2017 (Offline) Physics - Atoms and Nuclei Question 205 English

r = 1/3

r = 4/3

r = 2/3

r = 3/4

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MCQ (Single Correct Answer)

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Out of Syllabus

A radioactive nucleus A with a half life T, decays into a nucleus B. At t = 0, there is no nucleus B. At sometime t, the ratio of the number of B to that of A is 0.3. Then, t is given by :

$$t = {T \over {\log (1.3)}}$$

$$t = T\log (1.3)$$

$$t = {T \over 2}{{\log 2} \over {\log 1.3}}$$

$$t = T{{\log 1.3} \over {\log 2}}$$

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MCQ (Single Correct Answer)

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A hydrogen atom makes a transition from n = 2 to n = 1 and emits a photon. This photon strikes a doubly ionized lithium atom (z = 3) in excited state and completely removes the orbiting electron. The least quantum number for the excited state of the ion for the process is :