Atomic Physics Test

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Atomic Physics Test - 2

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Question 1
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Directions: The following question has four choices out of which ONLY ONE is correct.

De Broglie used Einstein's special theory of relatively together with Plank's quantum theory to establish the wave property of particles. He gave fundamental relationship ; where and p is wavelength and momentum respectively and h is Plank's constant. A de-Broglile wave associated with an electron can form a standing wave between the atoms arranged in a one dimensional array with node at each of the atomic sites. A standing wave is formed when the distance between the atoms of any array is d = 3A^o_^. A similar standing wave is again formed if d = 3.5 A^o but not for any intermediate value of d.
For thermal neutron at ordinary temperature, energy is given by relation E = kT, where K is Boltzman constant mass of Neutron is 1.67 10^–23 g.

The least value of d for which standing wave can be formed is

A
3 A^o

B
0.5 A^o

C
1 A^o

D
1.5 A^o

Solution

The min distance for which the standing wave would be formed would be equal to the min difference between the atomic spacings, which is 0.5 A^o.
Question 2
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Directions: The following question has four choices out of which ONLY ONE is correct.

De Broglie used Einstein's special theory of relatively together with Plank's quantum theory to establish the wave property of particles. He gave fundamental relationship ; where and p is wavelength and momentum respectively and h is Plank's constant. A de-Broglile wave associated with an electron can form a standing wave between the atoms arranged in a one dimensional array with node at each of the atomic sites. A standing wave is formed when distance between the atoms of any array is d = 3A^o. A similar standing wave is again formed if d = 3.5 A^o but not for any intermediate value of d.
For thermal neutron at ordinary temperature, energy is given by relation E = kT, where K is Boltzman's constant mass of Neutron is 1.6710^–23 g.

The energy of electron (in eV) to form this standing wave is

A
100 eV

B
300 eV

C
1200 eV

D
150 eV

Solution

The wavelength of the radiation would be given by Bragg's relation.
2d sin = n
Hence, using the relation, we get, = 1
From De Broglie's relation, E = = 150 eV, we get,
E = 150 eV
Question 3
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De Broglie used Einstein's special theory of relatively together with Plank's quantum theory to establish the wave property of particles. He gave fundamental relationship ; where and p is wavelength and momentum respectively and h is Plank's constant. A de-Broglile wave associated with an electron can form a standing wave between the atoms arranged in a one-dimensional array with node at each of the atomic sites. A standing wave is formed when the distance between the atom's of any array is d = 3A^o. A similar standing wave is again formed if d = 3.5 A^o but not for any intermediate value of d.

For thermal neutron at ordinary temperature, energy is given by relation E = kT, where K is Boltzman's constant and mass of neutron is 1.6710^–23 g.

De-Broglie wavelength associated with neutrons in thermal equilibrium with matter at 27^oC is

A
1.79 A^o

B
179 A^o

C
17.9 A^o

D
1790 A^o

Solution

The De Broglie wavelength can be given by
= = 1.79
Question 4
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Directions: The following question has four choices out of which ONLY ONE is correct.

The X-ray emission line of tungsten occurs at= 0.021 nm. What is the energy difference between K and L levels in its atoms?

A
0.51 MeV

B
1.2 MeV

C
59 keV

D
13.6 eV

Solution

_{(3) = 0.021 nm = 0.21}
Since correspondent to the transition of an electron from L-shell to K-shell, therefore
E_L – E_K = (in eV) = = ^{58928 eV}
Or E 59 keV
Question 5
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Two radioactive materials X₁ and X₂ have decay constants 10 and ^_,respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X₁ to that of X₂ will be 1/e after what time period?

A

B

C

D

Solution

Given =
or (Initially both have the same number of nuclei, say N₀)

or e =

or e =

or 9t = 1
or t =
Question 6
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A freshly prepared radioactive source of half life 2h emits radiation of intensity, which is 64 times of the permissible safe level. The minimum time after which it would be possible to work safely with this source is

A
6h

B
12h

C
24h

D
128h

Solution

From R = R₀
We have, I = 64
Or n = 6 = number of half lives
t = = 62 = 12h
Question 7
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Directions: The following question has five choices out of which ONLY ONE is correct.

What is the average K.E of a gas molecule at a temperature of 300 K?: (Boltsmann constant = 1.3810^–23 JK^–1)

A
6.2110^-21 J

B
2.32 * 10⁴ J

C
6.2410⁹ J

D
3.2110⁸ J

Solution

(a) kT = energy
1.3810^–23. 300 =E
E = 6.2110^-21 J
Question 8
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Directions: The following question has five choices out of which ONLY ONE is correct.

The activity of a radioactive element decreases to one third of the original activity A₀ in a period 9 years. After a further lapse of 9 years, its activity will be

A
A₀

B
A₀

C

D

Solution

in 9 years
in next 9 years
Question 9
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Two nucleons are at a separation of 1 Fermi. The net force between them is F₁ if both are neutrons, F₂ if both are protons and F₃ if one is proton and the other is a neutron. Which of the following is correct?

A
F₁ > F₂ > F₃

B
F₁ = F₃ > F₂

C
F₂ > F₁ > F₃

D
F₁ = F₂ > F₃

Solution
Question 10
1 / -0

Directions: The following question has five choices out of which ONLY ONE is correct.

Given below is a Cs. of electromagnetic spectrum and its mode of production. Which one does not match?

A
Gamma rays - Radioactive decay of the nucleus

B
Ultraviolet - Magnetron valve

C
Infra-red - Vibration of atoms and molecules

D
Radio wave - Rapid acceleration and deceleration of electrons in conducting wires

Solution

(B) - Ultraviolet - Magnetron valve
Magnetron is used to generate microwaves
Question 11
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A proton accelerated through a potential V has de-Broglie wavelength . Then, the de-Broglie wavelength of an -particle, when accelerated through the same potential V, is

A

B

C

D

Solution

Let the wavelength of the proton,
Now, -particle has a charge that is twice the charge of a proton and mass that is four times the mass of a proton.

Thus,
Question 12
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Directions: The following question has five choices out of which ONLY ONE is correct.

Two radioactive samples have decay constants 15 x and 3 x. If they have the same number of nuclei initially, the ratio of number of nuclei after a time is

A

B

C

D

Solution

-

=
Question 13
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Directions: The following question has five choices out of which ONLY ONE is correct.

If the mass defect of ₈O¹⁶ nucleus is 0.128 amu, then the binding energy per nucleon of oxygen is

A
8.2 MeV

B
7.45 MeV

C
7.3 MeV

D
7.1 MeV

Solution

- 7.45 MeV
= 7.45 MeV
Question 14
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¹⁴N₇ is bombarded with ⁴He₂. The resulting nucleus is ¹⁷O₈ with the emission of a/an

A
neutrino

B
antineutrino

C
proton

D
neutron

Solution

For the given reaction , we have

¹⁴N₇ + ⁴He₂ ¹⁶O₈ + ¹p₁Hence proton is emitted.
Question 15
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a-particles of energy 400 KeV are bombarded on nucleus of ₈₂Pb. In scattering of a -particles, its minimum distance from nucleus will be

A
0.59 nm

B
0.59 A⁰

C
5.9 pm

D
0.59 pm

Solution

0.59 A⁰