Assertion : X-rays cannot be diffracted by means of grating. Reason : X-rays does not obey Bragg's law.

If the assertion and reason both are false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

The stopping potential V for photoelectric emission from a metal surface is plotted along Y-axis and frequency n of incident light along X-axis. A straight line is obtained as shown. Planck's constant is given by [CPMT 1987; Similar to MP PMT 2000; Kerala PET 2001]

Make an angle \[2{{\sin }^{-1}}\,(0.72)\] with each other

Product of slope on the line and charge on the electron

Make an angle \[2{{\sin }^{-1}}\,(0.72)\] with each other

Product of Slope and mass of electron

In Thomson spectrograph experiment, four positive ions P,Q,R and S are situated on Y-X curve a shown in the figure

The specific charge of R and S are same

The velocities of R and S are same

In the graph given below. If the slope is \[4.12\times {{10}^{-15}}\]V-sec, then value of ?h? should be

\[6.6\times {{10}^{-31}}\] J-sec

\[6.6\times {{10}^{-34}}\]J-sec

In the following arrangement y = 1.0 mm, d= 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. The stopping potential V needed to stop the photo current will be

If assertion is true but reason is false.

Let \[{{\lambda }_{\alpha }}\], \[{{\lambda }_{\beta }}\] and \[{{{\lambda }'}_{\alpha }}\] denote the wavelengths of the X-rays of the \[{{K}_{\alpha }},\,{{K}_{\beta }}\] and \[{{L}_{\alpha }}\] lines in the characteristic X-rays for a metal

\[\frac{1}{{{\lambda }_{\alpha }}}+\frac{1}{{{\lambda }_{\beta }}}=\frac{1}{{{{{\lambda }'}}_{\alpha }}}\]

\[{{\lambda }_{\alpha }}>{{{\lambda }'}_{\alpha }}>{{\lambda }_{\beta }}\]

\[{{{\lambda }'}_{\alpha }}>{{\lambda }_{\beta }}>{{\lambda }_{\alpha }}\]

If assertion is true but reason is false.

\[\frac{1}{{{\lambda }_{\alpha }}}+\frac{1}{{{\lambda }_{\beta }}}=\frac{1}{{{{{\lambda }'}}_{\alpha }}}\]

Rest mass energy of an electron is 0.51 MeV. If this electron is moving with a velocity 0.8 c (where c is velocity of light in vacuum), then kinetic energy of the electron should be.

If assertion is true but reason is false.

A silver ball of radius 4.8 cm is suspended by a thread in the vacuum chamber. UV light of wavelength 200 nm is incident on the ball for some times during which a total energy of 1 ´ 10?7 J falls on the surface. Assuming on an average one out of 103 photons incident is able to eject electron. The potential on sphere will be

If assertion is true but reason is false.

The largest distance between the interatomic planes of a crystal is 10-7cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is [CPMT 1984]

If assertion is true but reason is false.

Ultraviolet light of wavelength 300 nm and intensity 1.0 watt/m2 falls on the surface of a photosensitive material. If 1% of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of 1.0 cm2 of the surface is nearly [AMU 1995]

\[2.13\times {{10}^{11}}per\ \sec \] per sec

\[9.61\times {{10}^{14}}per\ \sec \]per sec

\[4.12\times {{10}^{13}}per\ \sec \] per sec

If assertion is true but reason is false.

\[2.13\times {{10}^{11}}per\ \sec \] per sec

In a Thomson set-up for the determination of e/m, electrons accelerated by 2.5 \[kV\] enter the region of crossed electric and magnetic fields of strengths \[3.6\times {{10}^{4}}V{{m}^{-1}}\] and \[1.2\times {{10}^{-3}}T\] respectively and go through undeflected. The measured value of \[e/m\] of the electron is equal to [AMU 2002]

\[1.85\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]

\[1.0\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]

\[1.76\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]

If assertion is true but reason is false.

\[1.85\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]

Cathode rays consist of [DCE 1999]

If assertion is true but reason is false.

In Thomson experiment of finding \[e/m\] for electrons, beam of electron is replaced by that of muons (particle with same charge as of electrons but mass 208 times that of electrons). No deflection condition in this case satisfied if [Orissa (Engg.) 2002]

If assertion is true but reason is false.

Which of the following law is used in the Millikan's method for the determination of charge [DPMT 2002]

If assertion is true but reason is false.

An electron beam is moving between two parallel plates having electric field \[1.125\times {{10}^{-6}}N/m\]. A magnetic field \[3\times {{10}^{-10}}T\] is also applied so that beam of electrons do not deflect. The velocity of the electron is [MH CHT 2004]

If assertion is true but reason is false.

The kinetic energy of an electron which is accelerated through a potential of 100 volts is [MP PET 1986; CBSE PMT 1997; AIIMS 1998]

If assertion is true but reason is false.

\[6.626\times {{10}^{-34}}\]W- sec

A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength \[20\ V{{m}^{-1}}\]and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons [CBSE PMT 1996]

If assertion is true but reason is false.

In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is

If assertion is true but reason is false.

An electron is moving with constant velocity along \[x-\]axis. If a uniform electric field is applied along \[y-\]axis, then its path in the \[x-y\] plane will be [MP PMT 1999]

If assertion is true but reason is false.

The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by [MP PET 1994]

If assertion is true but reason is false.

When the speed of electrons increases, then the value of its specific charge [MP PMT 1994]

If assertion is true but reason is false.

Increases upto some velocity and then begins to decrease

Assertion : The specific charge of positive rays is not constant. Reason : The mass of ions varies with speed. [AIIMS 1999]

If assertion is true but reason is false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : The de-Broglie wavelength of a molecule varies inversely as the square root of temperature. Reason : The root mean square velocity of the molecule depends on the temperature. [AIIMS 1997]

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

25 + Mcqs in Photo Electric Effect, X- Rays & Matter Waves in Physics Page 1 McqOptions

1.	Assertion : X-rays cannot be diffracted by means of grating. Reason : X-rays does not obey Bragg's law.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

2.	The stopping potential V for photoelectric emission from a metal surface is plotted along Y-axis and frequency n of incident light along X-axis. A straight line is obtained as shown. Planck's constant is given by [CPMT 1987; Similar to MP PMT 2000; Kerala PET 2001]
A.	Slope of the line
B.	Product of slope on the line and charge on the electron
C.	Make an angle \[2{{\sin }^{-1}}\,(0.72)\] with each other
D.	Product of Slope and mass of electron
Answer» C. Make an angle \[2{{\sin }^{-1}}\,(0.72)\] with each other

Discussion

3.	In Thomson spectrograph experiment, four positive ions P,Q,R and S are situated on Y-X curve a shown in the figure
A.	The specific charge of R and S are same
B.	The masses of P and S are same
C.	90° ?A
D.	The velocities of R and S are same
Answer» B. The masses of P and S are same

Discussion

4.	In the graph given below. If the slope is \[4.12\times {{10}^{-15}}\]V-sec, then value of ?h? should be
A.	\[6.6\times {{10}^{-31}}\] J-sec
B.	\[6.6\times {{10}^{-34}}\]J-sec
C.	sin \[\theta \] \[\le \]2/3
D.	None of these
Answer» C. sin \[\theta \] \[\le \]2/3

Discussion

5.	The intensity distribution of X-rays from two coolidge tubes operated on different voltages V1 and V2 and using different target materials of atomic numbers Z1 and Z2 is shown in the figure. Which one of the following inequalities is true?
A.	V1 > V2, Z1 < Z2
B.	V1 > V2, Z1 > Z2
C.	4/3
D.	V1 = V2, Z1 < Z2
Answer» B. V1 > V2, Z1 > Z2

Discussion

6.	The figure represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote [CBSE PMT 1995]
A.	Band spectrum
B.	Continuous spectrum
C.	\[\sqrt{(3/2)}\]
D.	White radiations
Answer» D. White radiations

Discussion

7.	In the following arrangement y = 1.0 mm, d= 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. The stopping potential V needed to stop the photo current will be
A.	0.9 V
B.	0.5 V
C.	If assertion is true but reason is false.
D.	0.1 V
Answer» B. 0.5 V

Discussion

8.	Let \[{{\lambda }_{\alpha }}\], \[{{\lambda }_{\beta }}\] and \[{{{\lambda }'}_{\alpha }}\] denote the wavelengths of the X-rays of the \[{{K}_{\alpha }},\,{{K}_{\beta }}\] and \[{{L}_{\alpha }}\] lines in the characteristic X-rays for a metal
A.	\[{{\lambda }_{\alpha }}>{{{\lambda }'}_{\alpha }}>{{\lambda }_{\beta }}\]
B.	\[{{{\lambda }'}_{\alpha }}>{{\lambda }_{\beta }}>{{\lambda }_{\alpha }}\]
C.	If assertion is true but reason is false.
D.	\[\frac{1}{{{\lambda }_{\alpha }}}+\frac{1}{{{\lambda }_{\beta }}}=\frac{1}{{{{{\lambda }'}}_{\alpha }}}\]
Answer» D. \[\frac{1}{{{\lambda }_{\alpha }}}+\frac{1}{{{\lambda }_{\beta }}}=\frac{1}{{{{{\lambda }'}}_{\alpha }}}\]

Discussion

9.	Rest mass energy of an electron is 0.51 MeV. If this electron is moving with a velocity 0.8 c (where c is velocity of light in vacuum), then kinetic energy of the electron should be.
A.	0.28 MeV
B.	0.34 MeV
C.	If assertion is true but reason is false.
D.	0.46 MeV
Answer» C. If assertion is true but reason is false.

Discussion

10.	A silver ball of radius 4.8 cm is suspended by a thread in the vacuum chamber. UV light of wavelength 200 nm is incident on the ball for some times during which a total energy of 1 ´ 10?7 J falls on the surface. Assuming on an average one out of 103 photons incident is able to eject electron. The potential on sphere will be
A.	1 V
B.	2 V
C.	If assertion is true but reason is false.
D.	Zero
Answer» D. Zero

Discussion

11.	The largest distance between the interatomic planes of a crystal is 10-7cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is [CPMT 1984]
A.	1 Å
B.	2 Å
C.	If assertion is true but reason is false.
D.	20 Å
Answer» E.

Discussion

12.	Ultraviolet light of wavelength 300 nm and intensity 1.0 watt/m2 falls on the surface of a photosensitive material. If 1% of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of 1.0 cm2 of the surface is nearly [AMU 1995]
A.	\[9.61\times {{10}^{14}}per\ \sec \]per sec
B.	\[4.12\times {{10}^{13}}per\ \sec \] per sec
C.	If assertion is true but reason is false.
D.	\[2.13\times {{10}^{11}}per\ \sec \] per sec
Answer» D. \[2.13\times {{10}^{11}}per\ \sec \] per sec

Discussion

13.	In a Thomson set-up for the determination of e/m, electrons accelerated by 2.5 \[kV\] enter the region of crossed electric and magnetic fields of strengths \[3.6\times {{10}^{4}}V{{m}^{-1}}\] and \[1.2\times {{10}^{-3}}T\] respectively and go through undeflected. The measured value of \[e/m\] of the electron is equal to [AMU 2002]
A.	\[1.0\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]
B.	\[1.76\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]
C.	If assertion is true but reason is false.
D.	\[1.85\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]
Answer» D. \[1.85\times {{10}^{11}}C\text{-}k{{g}^{-1}}\]

Discussion

14.	Cathode rays consist of [DCE 1999]
A.	Photons
B.	Electrons
C.	If assertion is true but reason is false.
D.	\[\alpha \]-particles
Answer» C. If assertion is true but reason is false.

Discussion

15.	In Thomson experiment of finding \[e/m\] for electrons, beam of electron is replaced by that of muons (particle with same charge as of electrons but mass 208 times that of electrons). No deflection condition in this case satisfied if [Orissa (Engg.) 2002]
A.	B is increased 208 times
B.	E is increased 208 times
C.	If assertion is true but reason is false.
D.	None of these
Answer» D. None of these

Discussion

16.	Which of the following law is used in the Millikan's method for the determination of charge [DPMT 2002]
A.	Ampere's law
B.	Stoke's law
C.	If assertion is true but reason is false.
D.	Fleming's right hand rule
Answer» C. If assertion is true but reason is false.

Discussion

17.	An electron beam is moving between two parallel plates having electric field \[1.125\times {{10}^{-6}}N/m\]. A magnetic field \[3\times {{10}^{-10}}T\] is also applied so that beam of electrons do not deflect. The velocity of the electron is [MH CHT 2004]
A.	\[4225\ m/s\]
B.	\[3750\ m/s\]
C.	If assertion is true but reason is false.
D.	\[3200\ m/s\]
Answer» C. If assertion is true but reason is false.

Discussion

18.	The kinetic energy of an electron which is accelerated through a potential of 100 volts is [MP PET 1986; CBSE PMT 1997; AIIMS 1998]
A.	\[1.602\times {{10}^{-17}}J\]
B.	418.6 calories
C.	If assertion is true but reason is false.
D.	\[6.626\times {{10}^{-34}}\]W- sec
Answer» B. 418.6 calories

Discussion

19.	A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength \[20\ V{{m}^{-1}}\]and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons [CBSE PMT 1996]
A.	20 \[m{{s}^{-1}}\]
B.	40 \[m{{s}^{-1}}\]
C.	If assertion is true but reason is false.
D.	5.5 \[m{{s}^{-1}}\]
Answer» C. If assertion is true but reason is false.

Discussion

20.	In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is
A.	It is a lubricant
B.	Its density is higher
C.	If assertion is true but reason is false.
D.	It does not vapourise
Answer» E.

Discussion

21.	An electron is moving with constant velocity along \[x-\]axis. If a uniform electric field is applied along \[y-\]axis, then its path in the \[x-y\] plane will be [MP PMT 1999]
A.	A straight line
B.	A circle
C.	If assertion is true but reason is false.
D.	An ellipse
Answer» D. An ellipse

Discussion

22.	The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by [MP PET 1994]
A.	Planck
B.	J.J. Thomson
C.	If assertion is true but reason is false.
D.	Millikan
Answer» E.

Discussion

23.	When the speed of electrons increases, then the value of its specific charge [MP PMT 1994]
A.	Increases
B.	Decreases
C.	If assertion is true but reason is false.
D.	Increases upto some velocity and then begins to decrease
Answer» C. If assertion is true but reason is false.

Discussion

24.	Assertion : The specific charge of positive rays is not constant. Reason : The mass of ions varies with speed. [AIIMS 1999]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» C. If assertion is true but reason is false.

Discussion

25.	Assertion : The de-Broglie wavelength of a molecule varies inversely as the square root of temperature. Reason : The root mean square velocity of the molecule depends on the temperature. [AIIMS 1997]
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

Explore topic-wise MCQs in Physics.

Assertion : X-rays cannot be diffracted by means of grating. Reason : X-rays does not obey Bragg's law.

The stopping potential V for photoelectric emission from a metal surface is plotted along Y-axis and frequency n of incident light along X-axis. A straight line is obtained as shown. Planck's constant is given by [CPMT 1987; Similar to MP PMT 2000; Kerala PET 2001]

In Thomson spectrograph experiment, four positive ions P,Q,R and S are situated on Y-X curve a shown in the figure

In the graph given below. If the slope is \[4.12\times {{10}^{-15}}\]V-sec, then value of ?h? should be

The intensity distribution of X-rays from two coolidge tubes operated on different voltages V1 and V2 and using different target materials of atomic numbers Z1 and Z2 is shown in the figure. Which one of the following inequalities is true?

The figure represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote [CBSE PMT 1995]

In the following arrangement y = 1.0 mm, d= 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. The stopping potential V needed to stop the photo current will be

Let \[{{\lambda }_{\alpha }}\], \[{{\lambda }_{\beta }}\] and \[{{{\lambda }'}_{\alpha }}\] denote the wavelengths of the X-rays of the \[{{K}_{\alpha }},\,{{K}_{\beta }}\] and \[{{L}_{\alpha }}\] lines in the characteristic X-rays for a metal

Rest mass energy of an electron is 0.51 MeV. If this electron is moving with a velocity 0.8 c (where c is velocity of light in vacuum), then kinetic energy of the electron should be.

The largest distance between the interatomic planes of a crystal is 10-7cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is [CPMT 1984]

Ultraviolet light of wavelength 300 nm and intensity 1.0 watt/m2 falls on the surface of a photosensitive material. If 1% of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of 1.0 cm2 of the surface is nearly [AMU 1995]

Cathode rays consist of [DCE 1999]

In Thomson experiment of finding \[e/m\] for electrons, beam of electron is replaced by that of muons (particle with same charge as of electrons but mass 208 times that of electrons). No deflection condition in this case satisfied if [Orissa (Engg.) 2002]

Which of the following law is used in the Millikan's method for the determination of charge [DPMT 2002]

An electron beam is moving between two parallel plates having electric field \[1.125\times {{10}^{-6}}N/m\]. A magnetic field \[3\times {{10}^{-10}}T\] is also applied so that beam of electrons do not deflect. The velocity of the electron is [MH CHT 2004]

The kinetic energy of an electron which is accelerated through a potential of 100 volts is [MP PET 1986; CBSE PMT 1997; AIIMS 1998]

A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength \[20\ V{{m}^{-1}}\]and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons [CBSE PMT 1996]

In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is

An electron is moving with constant velocity along \[x-\]axis. If a uniform electric field is applied along \[y-\]axis, then its path in the \[x-y\] plane will be [MP PMT 1999]

The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by [MP PET 1994]

When the speed of electrons increases, then the value of its specific charge [MP PMT 1994]

Assertion : The specific charge of positive rays is not constant. Reason : The mass of ions varies with speed. [AIIMS 1999]

Assertion : The de-Broglie wavelength of a molecule varies inversely as the square root of temperature. Reason : The root mean square velocity of the molecule depends on the temperature. [AIIMS 1997]