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Revision Quiz on Atoms and Nuclei

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Question 1

At some instant, a radioactive sample having an activity 5 μCi has twice the number of nuclei as another sample which has an activity of 10 μCi. The half lives of and are :

Question 2

A photon of wavelength is absorbed by an electron confined to a box of length As a result the electron makes a transition from state k=1 to the state n. Subsequently the electron transis from the state n to the state m by emitting a photon of wavelength = 1.75. Then

Question 3

A radioactive sample has 27×1020 atoms at time t=0. It reduces to 1/3 in number in 10 sec. How many atoms of the sample will decay in time interval 20<t<30 sec?

Question 4

A radioactive source contains two radioisotopes, each with initial activity (1 Bq = 1 Becquerel = 1 decay per second). The half-life of one of the radioisotopes is one hour and that of the other is two hours. Calculate how many nuclei decay in the period of first four hours?

Question 5

A piece of wood from a recently cut tree shows 20 decays per minute. A wooden piece of same size placed in a museum (obtained from a tree cut many years back) shows 2 decays per minute. If half life of is 5730 years, then age of the wooden piece placed in the museum is approximately:

Question 6

X-rays of wavelength 0.140 nm are scattered from a block of carbon. What will be the wavelengths of X-rays scatterd at 900 ?

Question 7

Suppose that the potential energy of an hypothetical atom consisting of a proton and an electron is given by U = – ke2/3r3. Then if Bohr's postulates are applied to this atom, then the radius of the nth orbit will be proportional to

Question 8

Two elements A and B with atomic numbers ZA and ZB are used to produce characteristic x-rays with frequencies vA and vB respectively. If ZA : ZB = 1:2, then vA : vB will be

Question 9

Assume that a neutron breaks into a proton and an electron. The energy released during this process is (Mass of neutron = 1.6725 × 10–27) kg; mass of proton = kg; mass of electron = kg)

Question 10

If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li++ is

Question 11

In a hydrogen like atom electron makes transition from an energy level with quantum number n to another with quantum number
(n – 1). If n >> 1, the frequency of radiation emitted is proportional to

Question 12

Starting with a sample of pure 66Cu, 7/8 of it decays into Zn in 15 minutes. The corresponding half-life is

Question 13

This question contains Statement-1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.
STATEMENT – 1: Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion.
STATEMENT – 2: For heavy nuclei, binding energy per nucleon increases with increasing Z while for light nuclei it decreases with increasing Z.

Question 14

Suppose an electron is attracted towards the origin by a force , where k is a constant and r is the distance of the electron from the origin. By applying Bohr model to this system, the radius of the nth orbital of the electron is found to be rn and the kinetic energy of the electron to be Tn. Then which of the following is true?

Question 15

In the hydrogen atom, the ratio of wavelength of the Lyman-β transition to Balmer-β transition is
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Mar 18JEE & BITSAT