MCQ Questions for Class 12 Medical Physics Atoms Quiz 3

If an element has 22 electrons then what will be its atomic number?

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10
0%
25
0%
15
0%
22

If an element X has mass number and number of proton 8 then identify element X

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C
0%
N
0%
O
0%
Ar

An element necessarily have same

0%
No. of protons
0%
No. of electrons
0%
No. of nuetrons
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All

Explanation

$Answer:-$ A

For isotopes we say they have atomic number.

Isotopes are atoms with the same number of protons but that have a different number of neutrons. Since the atomic number is equal to the number of protons and the atomic mass is the sum of protons and neutrons, we can also say that isotopes are elements with the same atomic number but different mass .

Smallest particle in a chemical element or compound that has the chemical properties of that element or compound is

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Atom
0%
Molecule
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Mixture
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Element

An element X has mass number 10, and number of neutrons =Then what will be the number of proton?

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10
0%
3
0%
7
0%
17

Explanation

Mas number of any element is equal to sum of proton and neutrons

$\therefore A = p+n$
So,

$p=A-n= 10-7=3$

What is the mass of neutron?

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$1.675\times 10^{-24}g$
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$9.1\times 10^{-31} kg$
0%
$1.675\times 10^{-30}g$
0%
$9.1\times 10^{-27}kg$

Explanation

Mass of neutron is

$1.675\times 10^{-24}g$ which is nearly the same as that of hydrogen atom.

Packets of which of the following quantity best describe photons ?

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energy
0%
mass
0%
volume
0%
power
0%
waves

Explanation

Modern physicists demonstrate that energy in an electromagnetic field is made up of discrete packets. These packets are of energy are termed as photons. This is the reason behind the particle like behavior of light.

Energy of each photon in a wave of wavelength

$\lambda$ is

$E=\dfrac{hc}{\lambda}$ .

What is the electronic configuration of phosphorus?

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2, 8, 5
0%
2, 8, 4
0%
2, 8, 6
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2, 8, 3

A substance consisting of atoms which all have the same number of protons is called a/an

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Element
0%
Molecule
0%
Mixture
0%
Solution

$U^{235}, U^{238}, U^{239}$ are the atoms of the uranium. Which are called as

0%
Isomers
0%
Isobars
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Isotopes
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None of these

Explanation

Isotopes are the same element which have same atomic number but different mass numbers.

$U^{235}, U^{238}, U^{239}$ all have different mass numbers.

Which instrument was used for the discovery of the electron?

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Plum Pudding Model
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Oil Drop Apparatus
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Gold Foil Experiment
0%
Alpha Particle Emitter
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Cathode Ray Tube

What is the correct order in which the listed atomic models were advanced and accepted, earliest first?

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Bohr, planetary, plum pudding
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Planetary, Bohr, plum pudding
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Plum pudding, Bohr, planetary
0%
Plum pudding, planetary, Bohr
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Planetary, plum pudding, Bohr

Spectrum of sunlight is an example for

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Band emission spectrum
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Line absorption spectrum
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Continuous emission spectrum
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Continuous absorption spectrum

Which of the following can produced emission spectrum ?

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electrons in an excited gas jump up to a higher energy level and release photons.
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electrons in an excited gas jump down to a lower energy level and release photons.
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electrons are released from the outer orbitals of an excited gas.
0%
an unstable nucleus releases energy.
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light is shined on a metal surface and electrons are released.

Which of the following is NOT a postulate of Bohr's model of the hydrogen atom?

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Gases excited by a voltage emits a bright-light emission spectrum.
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The position of an electron in the hydrogen atom is not defined.
0%

Electron absorbs energy to make transition to a higher energy level.
0%

Electron emits energy when it makes transition to a lower energy level.
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The energy levels of the electron are quantized.

The concept of stationary orbits was proposed by.

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J. J. Thomson
0%
Rutherford
0%
Neil Bohr
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LNewton

Identify which of the following is the smallest discrete value of electromagnetic energy ?

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photon
0%
proton
0%
electron
0%
neutron
0%
quark

Which of the following conclusions can be drawn from the Rutherford alpha scattering model?

I. The atom is mostly empty space.
II. Electrons orbit the nucleus of the atom.
III. The atom has a dense, positively charged nucleus.

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I only
0%
II only
0%
I and II only
0%
II and III only
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I, II, and III

The size of the nucleus varies as __________ power of the atomic number.

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$1/2$
0%
$2$
0%
$1/3$
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$3$

Explanation

We know that the cube of radius of nucleus is directly proportional to the atomic mass.

$R^3\alpha A$

$R\alpha A^{\frac13}$

$R=R_0A^{\frac13}$

Where,

$R$ is the Radius of the nucleus

$R_0$ is Fermi Constant

So, the radius of a nucleus is proportional to the cube root of its mass number.

According to the quantum theory of light, the energy of light is carried in discrete units called

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alpha particles
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photoelectrons
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protons
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photons

In a laser tube, all the photons

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have same wavelength
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have same energy
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move in same direction
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move with same speed.

Explanation

The photon produced in a laser move at the speed of light and it is constant for all the photons.

$(c = 3\times10^8 m/s)$ .

Practically the light from the laser has slight variations in their wavelength and the frequency. So, they cannot be same.

According to Bohr's model of hydrogen atom, relation between principal quantum number n and radius of stable orbit is

0%
$r \propto \frac{1}{n}$
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$r \propto n$
0%
$r\propto\frac{1}{n^2}$
0%
$r\propto n^2$

Explanation

Let an electron (mass m), is revolving around nucleus of a hydrogen atom in an orbit of radius

$r$ with velocity

$v$ . Electron gets centripetal force to revolve, from the electrostatic attraction force between electron and nucleus,

$\dfrac{mv^{2}}{r}=\dfrac{e\times e}{4\pi\varepsilon_{0}r^{2}}$ (for H- atom,

$Z=1$ hence charge on nucleus is

$=e$ )

$mv^{2}=\dfrac{e^{2}}{4\pi\varepsilon_{0}r}$ ...................eq1

According to Bohr's model, angular momentum of electron :

$mvr=\dfrac{nh}{2\pi}$ ..................eq2

Now, squaring eq2 and dividing by eq1, we get

$\dfrac{mv^{2}r^{2}}{mv^{2}}=\dfrac{n^{2}h^{2}4\pi\varepsilon_{0}r}{4\pi^{2}e^{2}}$

$r=\dfrac{n^{2}h^{2}\varepsilon_{0}}{\pi me^{2}}$

which gives

$r\propto n^{2}$

In a cathode ray oscillograph, the focusing of beam on the screen is achieved by

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Convex lens
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Magnetic field
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Electric potential
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All of these

When electron remains between orbits, its momentum is :

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quantized
0%
dequantized
0%
emitted
0%
changed always

Number of spectral lines in hydrogen atom is

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$8$
0%
$6$
0%
$15$
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$\infty$

Explanation

Number of spectral lines in hydrogen atom

$\infty$ .

When electron changes its orbit from outer to inner energy is :

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absorbed
0%
released
0%
no change
0%
remains constant

When an electron jumps from its orbit to another orbit, energy is :

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emitted
0%
absorbed
0%
both absorbed and emitted
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depends on the energy levels of the orbits

Orbits in which electrons move according to Bohr are :

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elliptical
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cylindrical
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circular
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oval

Particles having half integral spin are :

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Electron
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Photon
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Proton
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Neutron

Explanation

Electrons, protons as well as neutrons have integral half spin i.e.

$\dfrac{1}{2}$ or

$-\dfrac{1}{2}$
Whereas photons as integral spin i.e.

$1$
So, options A, C and D are correct.

In the discharge tube as the density of atom increases, the intensity spectral lines

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Decreases continuously
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Increases continuously
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Remains constant
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None of these

Which spectrum is continuous

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$\alpha$ -rays
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$\beta$ -rays
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$\gamma$ -rays
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All of these

Explanation

$\beta \; rays$ spectrum is continuous among

$\alpha$ and

$\gamma$ rays spectrum.

Line spectrum contains information about the :

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Atoms of the prism
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Atoms of the source
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Molecules of the source
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Atoms as well as molecules of the source

In an atom an electron excites to the fourth orbit.When it jumps back to the energy level one a spectrum is formed. Total number of spectral lines in this spectrum would be

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3
0%
4
0%
5
0%
6

Explanation

The relation to find number of spectral lines is $\frac{({{n}_{2}}-{{n}_{1}})({{n}_{2}}-{{n}_{1}}+1)}{2}$

Here transition is from n = 4 to n = 1

So, number of spectral lines = $\frac{3\times 4}{2}=6$

Hence, there are 6 spectral lines.

An electron jumps from

$6^{th}$ shell in an hydrogen atom, the number of Lyman emission lines will be:

0%
5
0%
6
0%
10
0%
12

Explanation

From level 6 to level 1 i,e,

$6 \rightarrow 1$

and

$5 \rightarrow 1$

$4 \rightarrow 1$

$3 \rightarrow 1$

$2\rightarrow 1$

So total 5 lines in Lyman series.

Cathode rays ___________.

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Are the atoms moving toward the cathode
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Are electromagnetic waves
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Are negative ions travelling from cathode to anode
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Are electrons emitted by cathode and travelling towards anode

When an alpha particle is emitted from a radioactive source.

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Its atomic number increases by $4$
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Its atomic number decreases by $2$
0%
Its atomic number increases by $2$
0%
It atomic number decreases by $4$

What is the wavelength of the most energetic photon emitted in the Balmer's series of the hydrogen atom?

0%
$3694 \ A$
0%
$5756 \ A$
0%
$3333 \ A$
0%
$3669 \ A$

Explanation

Balmer series means wavelength is given by

$\dfrac{1}{\lambda}=R(\dfrac{1}{4}-\dfrac{1}{n^2})$

for maximum wavelength the

$n$ should be max so putting

$n\rightarrow \infty$

we get

$\lambda=\dfrac{4}{R}$

putting the Rydberg's constant as

$R=1.09\times 10^{7} /m$

we get

$\lambda= 3669\times 10^{-10}meter=3669Angstrom$

'Electrons revolve round the nucleus in well-defined orbits, like planets revolve round the sun' was the brainchild of.

0%
Arnold Sommerfeld
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Max Born
0%
Ernest Rutherford
0%
Niels Bohr

Explanation

$\begin{array}{l}\text { Electron revolves around the nucleus in wall-defined } \\\text { orbits, like planets revolve around the sun was } \\\text { the brainchild of Niels Bohr. }\end{array}$

Which one of the following device makes use of the electrons to strike certain substances to produce fluorescence?

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Thermionic value
0%
Photoelectric cell
0%
Cathode ray oscilloscope
0%
Electron gun

The number of significant figure in

$6.023 \times 10 ^ { 23 } \mathrm { mole } ^ { - 1 }$ is

0%
4
0%
3
0%
2
0%
23

Explanation

The number of significant figure in

$6.023\times { 10^{ 23 } }{ { mol } }{ { { e } }^{ -1 } }$ is

$as\, Avogadros\quad number\, ,\, 4\, \quad is\quad \, significant\, \quad figures$

so the corecct option is A.

The number of orbitals in

$n=3$ are :

0%
$1$
0%
$4$
0%
$9$
0%
$16$

Explanation

Given :

No. of shells

$\left( n \right) = 3$

Formula to calculate the number of orbitals is, number of orbitals

$= {n}^{2}$

$\therefore \text {Number of orbitals} =$

${n}^{2} = {\left( 3 \right)}^{2} = 9$

Therefore, the option is

$C$ .

To which of the following the angular velocity of the electron in the n-th Bohr orbit is proportional ?

0%
$n^2$
0%
$\dfrac{1}{n^2}$
0%
$\dfrac{1}{n^{\dfrac{3}{2}}}$
0%
$\dfrac{1}{n^3}$

Explanation

$L=mr^2\omega=\dfrac{nh}{2\pi},\omega \propto \dfrac{n}{r^2}$

$,\omega\propto \dfrac{n}{(r_0n^2)^2},\omega\propto \dfrac{1}{n^3}$

Cathode rays constitute a stream of

0%
electrons
0%
protons
0%
positive ions
0%
negative ions.

Two photons having _________________.

0%
Equal wavelengths have equal linear momenta
0%
Equal energies have equal linear momenta
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Equal frequencies have equal linear momenta
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Equal linear momenta have equal wavelengths

The radius of a shell for

$H-atom$ is

$4.761\,\overset{o}{A}$ . The value of n is:

0%
3
0%
9
0%
5
0%
None of these

Explanation

We know, Bhor's radius

$r_{n} = 52.9n^{2}$ Pm

$\rightarrow (1)$

As we are given,

$r_{n} = 4.761\dot{A}$

$\rightarrow (2)$

equating both the equations

$4.761\times 10^{-10} = 52.9 n^{2}\times 10^{-10}$

$n^{2} = 9$

$n = 3$

1195383_1340820_ans_82a6ad1e3ef24e149c0083ec4d5555d2.jpg

Which of the following samples will have the same number of atoms as 40 g calcium?

0%
24 g magnesium
0%
64 g silphur
0%
14 g nitrogen
0%
8 g oxygen

Explanation

Molar mass of $Ca=M`= 40$

Molar mass of $Mg=M=24$

Given mass of $Ca= m`=40g$

Given mass of $Mg=m=?$

Formula: $m= m`× M/ M`$

$m= 40\times \dfrac{24}{40}$

$m= 24g$

Cathode rays are passing through a discharge tube. In the tube, there is

0%
an electric field but no magnetic field
0%
a magnetic field but no electric field
0%
an electric as well as a magnetic field
0%
neither an electric nor a magnetic field.

The band spectra (characteristic of molecular species) is due to emission of radiation

0%
Solid state
0%
All of three states
0%
Gaseous state
0%
Liquid state

Emission spectrum of

$CO_{2}$ gas

0%
Is a line spectrum
0%
Is a band spectrum
0%
Is a continuous spectrum
0%
Does not fall in the visible region

Explanation

The emission spectrum of

$CO_2$ gas that has been studied by the electron beam excitation method is a band spectrum.

Consider the following two statements

$A$ and

$B$ and identify the correct choice in the given answers

$A :$ Line spectra is due to atoms in gaseous state

$B :$ Band spectra is due to molecules

0%
Both $A$ and $B$ are false
0%
$A$ is true and $B$ is false
0%
$A$ is false and $B$ is true
0%
Both $A$ and $B$ are true

CBSE Questions for Class 12 Medical Physics Atoms Quiz 3 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

CBSE Questions for Class 12 Medical Physics Atoms Quiz 3 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

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