159 + Interview Questions in ELECTRONS-AND-PHOTONS IN GENERAL AWARENESS Page 3 InterviewSolution

101.	An electron is fired through a region of crossed electric and magnetic field (0.05 T) . The electric field is formed between two plates separated by a distance of 2 mm having a P.D. of 125 V . The speed of the electron isA. `12.5 xx 10^(6)` m/sB. `1250 ` K m/sC. 125 K m/sD. `1.25 xx 10^(7)` m/s
Answer» Correct Answer - B

Discussion

102.	If the threshold wavelength for a certain metal is `2000Å`, then the work function of the metal isA. `6.2`JB. `6.2eV`C. `6.2MeV`D. `6.2Ev`
Answer» Correct Answer - D

Discussion

103.	The number of photons required to give a definite energy W variesA. inversely as the frequencyB. directly as the frequencyC. independent of the frequencyD. inversely as the wavelength
Answer» Correct Answer - A

Discussion

104.	The wavelength of an electron , moving with the velocity `3 xx 10^(3)` m/s , is nearly equal toA. `2xx10^(-12) `mB. `6 xx 10^(-13)` mC. `2.5 xx 10^(-7)` mD. `8 xx 10^(-10)`m
Answer» Correct Answer - A

Discussion

105.	The dual nature of matter was predicted byA. EinsteinB. ComptonC. de BroglieD. Thomson
Answer» Correct Answer - C

Discussion

106.	A quantum of light energy is calledA. protonB. photonC. electronD. neutron
Answer» Correct Answer - B

Discussion

107.	The momentum of moving particle is p . The wavelength `lambda` of the associated matter wave will beA. h/pB. hpC. p/hD. p
Answer» Correct Answer - A

Discussion

108.	The work function of a substance is `1.6 eV`. The longest wavelength of light that can produce photoemisson form the substance isA. 2900 ÅB. 3867 ÅC. 5800 ÅD. 7734 Å
Answer» Correct Answer - D

Discussion

109.	In photoelectric effectA. light energy is converted into the heat energyB. light is converted into electric energyC. light energy is converted into the sound energyD. electric energy is converted into light energy
Answer» Correct Answer - B

Discussion

110.	The rest mass of a photon of wavelength `lambda` isA. ZeroB. `h// c lambda`C. `h// lambda`D. `hc//lambda`
Answer» Correct Answer - A

Discussion

111.	The momentum of a photon of wavelength `lambda` isA. `h lambda`B. `h//lambda`C. ` lambda//h `D. `h//c lambda`
Answer» Correct Answer - B

Discussion

112.	The energy of a photon of wavelength `lambda` is given byA. `hc lambda`B. `h c//lambda`C. `lambda//hc `D. `h lambda//c`
Answer» Correct Answer - B

Discussion

113.	The idea of the quantum nature of light has emerged in an attempt to explainA. radioactivityB. thermionic emissionC. interference of lightD. thermal radiations of a black body
Answer» Correct Answer - D

Discussion

114.	A photon in motion has a massA. c/hvB. h/vC. hvD. `hv//c^(2)`
Answer» Correct Answer - D

Discussion

115.	A metal surface is illuminated by the protons of energy 5 eV and 2.5 eV respectively . The ratio of their wavelength isA. `1 : 3`B. `1 : 4`C. `1 : 2`D. `2 :1`
Answer» Correct Answer - C

Discussion

116.	The energy radiated from a source is in the form ofA. atomsB. photonsC. deuteronsD. electrons
Answer» Correct Answer - B

Discussion

117.	The amount of energy radiated by a body depends uponA. the area of the surfaceB. the temperature of its surfaceC. the nature of its surfaceD. all of these
Answer» Correct Answer - D

Discussion

118.	Photoelectric cell is a device in which the light energy is converted intoA. heat energyB. mechanical energyC. electric energyD. kinetic energy
Answer» Correct Answer - C

Discussion

119.	The strength of the photoelectric current depends uponA. frequency of incident radiationB. intensity of incident radiationC. angle of incident radiationD. distance between anode and cathode
Answer» Correct Answer - B

Discussion

120.	The maximum number of the photoelectrons , released in a photocell , is independent ofA. nature of the cathode surfaceB. frequency of the incident lightC. intensity of the radiationsD. whether of the atmosphere
Answer» Correct Answer - B

Discussion

121.	The use of photoelectric cell in cinema depends upon the fact that the number of electrons produced is directly proportional toA. charge of electronsB. wavelength of lightC. intensity of lightD. all of these
Answer» Correct Answer - C

Discussion

122.	The stopping potential for the photoelectrons , from a photocell , is proportionalA. directly on the intensity of incident lightB. inversely to the intensity of incident lightC. directly to the frequency of incident lightD. inversely to the frequency of incident light
Answer» Correct Answer - C

Discussion

123.	In photoelectric cell ,the electrons leave the surface with maximum energy , which areA. just on the surfaceB. just below the surfaceC. 2 mm above the surfaceD. 2 mm below the surface
Answer» Correct Answer - A

Discussion

124.	When an inert gas is filled in the place vacuum in a photo cell , thenA. photo current will decreaseB. photo current will increaseC. photo current remains the sameD. photo current does not depend upon the filled gas
Answer» Correct Answer - B

Discussion

125.	When a beam of electrons passes through an electrostatic field of `300 V cm^(-1)` at right angles to the direction of field, it describes a circular path of radius `8 cm`. On entering the magnetic field of `15` oersted at right angles to the electrostatic field, the beam remains undeflected. Find specific charge of the electron.
Answer» Correct Answer - `1.67 xx 10^(11) C kg^(-1)`

Discussion

126.	Light of two different frequencies whose photons have energies 1eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum kinetic energy of emitted electrons will be:A. `1:2`B. `1:1`C. `1:5`D. `1:4`
Answer» Correct Answer - A

Discussion

127.	The photoelectrons emitted from a given cathode , on the incidence of a given monochromatic beam of light haveA. an energy spread with a lower limitB. an energy spread with an upper limitC. an energy spread with no sharp limitD. a definite energy only
Answer» Correct Answer - B

Discussion

128.	Photoelectrons are emitted by a metal surface only whenA. the frequency of incident light exceeds a certain minimum valueB. the wavelength of the incident light exceeds a certain minimum valueC. the light is incident at an angle greater than the critical angleD. the metal is initially charged
Answer» Correct Answer - A

Discussion

129.	The electrons are emitted in a photoelectric effect from a metal surfaceA. only if the frequency of radiation is above a certain threshold valueB. only if the temperature of surface is lowC. at a rate that is independent of the nature of metalD. with a maximum velocity proportional to the frequency of incident radiation .
Answer» Correct Answer - A

Discussion

130.	Photo electric effect is the phenomenon in whichA. photons come out of a metal when it is hit by a beam of electronsB. photons come out of the nucleus of an atom under the action of an electric fieldC. electrons come out of a metal with a constant velocity depends upon frequency and intensity of incident lightD. electrons come out of a metal with different velocities not greater than a certain value which depends only on the frequency of the incident wave and not its intensity
Answer» Correct Answer - D

Discussion

131.	If the kinetic energy of the particle is increased to `16` times its previous value , the percentage change in the de - Broglie wavelength of the particle isA. 25B. 75C. 60D. 50
Answer» Correct Answer - B

Discussion

132.	Threshold wavelength for photoelectric effect on sodium is `5000 Å` . Its work function isA. `4 xx 10^(-19) J`B. `1 J`C. `2 xx 10^(-19)` JD. `3 xx 10^(-19)` J
Answer» Correct Answer - A

Discussion

133.	Threshold wavelength for photoelectric effect on sodium is `5000 Å` . Its work function isA. 15 JB. `16 xx 10^(-14) J`C. `4 xx 10^(-19) J`D. `4 xx 10^(-18) J`
Answer» Correct Answer - C

Discussion

134.	A metal has a threshold wavelength fo `6000 Å`. Calculate (i) threshold frequency (ii) work function. Will there be photoelectric emission or not ?
Answer» Correct Answer - (i) `5 xx 10^(14)` Hz (ii) 2.07 eV

Discussion

135.	An electron is accelerated through a potential difference of `1000 V` and directed into space between two parallel plates separated by `2 cm` with a potential difference of `100 V` applied across them. If the electron enters perpendicular to the electric field between the polates, what magnetic field perpendicular to both the electron path and the electric field will be neccessary so that the electron may travel undeflected. Take `e=1.6xx10^(-19) C` and `m=9xx10^(31)kg`.
Answer» Correct Answer - `2.65 xx 10^(-4) Wbm ^(-2)`

Discussion

136.	Two parallel horizontal plane plates are `30 mm` long and `10 mm` apart. A fine horizontal beam of electrons, moving with a velocity of `5xx10^(6)ms^(-1)` enters the plates mid-way and produces a bright spot of light on a vertical screen `100 mm` beyond the edges of the plates. A potential difference of `10 V` is applieed to the plates. Calculate the deflection of the spot from its initial position.
Answer» Correct Answer - 24.5 mm

Discussion

137.	A narrow beam of electrons, accelerated by a potential difference of `250 V`, passes between two parallel metal plates `0.030 m` long and `0.005 m` apart in an evacuated tube and then strikes a fluorescent screen `0.175 m` from the centre of the plates. A potential difference of `10 V` is established between the plates. What is the deflection produced on the screen.
Answer» Correct Answer - 0.02 m

Discussion

138.	Monochromatic X-rays, when reflected from a crystal with lattice spacing `2.0 Å`, produce first order diffraction maximum at `theta=30^(@)`. What is the wavelength of X-rays ?
Answer» Correct Answer - `2.0 Å`

Discussion

139.	A beam of electrons is under the effect of potential difference of `1.36xx10^(4)` volt applied across two parallel plates `4 cm` apart and a magnetic field of `0.002 Wbm^(-2)` at right angles to each other. If these two field produces no deflection in the beam. find the velocity of electrons. What will be radius of the orbit in which the beam will move, if the electric field is made zero ? Given, Mass of electron `=9.1xx10^(-31)kg`.
Answer» Correct Answer - `1.7 xx 10^(8) ms^(-1), 0.4834 m`

Discussion

140.	What voltage must be applied to an electron microscope to produce electrons of wavelength `0.4A`?
Answer» Correct Answer - 940.6 V

Discussion

141.	What is the energy of emitted photoelectrons is light of frequency `10^(16) Hz` is incident on a sodium target ? Work function of sodium is = 2.5 eV.
Answer» Correct Answer - 38.875 eV

Discussion

142.	An electron moving at the speed of `10^(7)` m/s , enters a magnetic field of induction 0.1 T at right angle to the velocity of electron . The radius of circular path followed by the electron isA. 0.57 cmB. 5.7 cmC. 0.57 mmD. 0.27 mm
Answer» Correct Answer - C

Discussion

143.	An electron experiences a force equal to its weight, when placed in an electric field. The intensity of the field will beA. `1.7 xx 10^(-11)` N/CB. `5 xx 10^(-11) ` N/CC. `17 xx 10^(-11)` N/CD. `50 xx 10^(-11)` N/C
Answer» Correct Answer - B

Discussion

144.	For a certain metal `v = 2 v_(0)` and the electrons come out with a maximum velocity of `4 xx 10^(6)` m/s . If the value of ` v = 5 v_(0)` , then maximum velocity of the photoelectrons will beA. `8 xx 10^(5)` m/sB. `2 xx 10^(6)` m/sC. `8 xx 10^(6)` m/sD. `2 xx 10^(7)` m/s
Answer» Correct Answer - C

Discussion

145.	The energy of incident radiation, which emits the electrons with a velocity of `2.5 xx 10^(6)` m/s and work function 1.8 e V , isA. `1.937` eVB. 2 e VC. 19.57 e VD. 20.1 eV
Answer» Correct Answer - C

Discussion

146.	An electron of work function 1.4 eV is emitted with a velocity `5 xx 10^(6)` m/s . The wavelength of the incident radiation isA. `0.017` ÅB. 1.7 ÅC. 17 ÅD. 170 Å
Answer» Correct Answer - D

Discussion

147.	Mutually perpendicular electric and magnetic fields are given by E = 1500 V/m and B = 0.04 T . Then velocity is given byA. 60 m/sB. `3.75 xx 10^(6)` m/sC. `3.75 xx 10^(4)` m/sD. `60 xx 10^(4)` m/s
Answer» Correct Answer - C

Discussion

148.	When light of 2.5 eV falls on a metal surface, maximum kinetic energy of electron is T. If incident radiation of 4 eV falls on same metal surface, maximum kinetic energy of electrons is doubled. The work function of metal isA. 1 eVB. 4 e VC. 1.5 eVD. 0.5 eV
Answer» Correct Answer - A

Discussion

149.	The radiations of 1 eV and 2.5 eV are incident on a metal having a work function of 0.5 eV . The ratio of their maximum velocities isA. `(1)/(2)`B. `(1)/(4)`C. `(2)/(5)`D. `sqrt((5)/(2))`
Answer» Correct Answer - A

Discussion

150.	Which of the following graphs represents correctly the variations of `0.5 mv_("max")^(2)` with the intensity of incident radiations of a constant frequency ?A. B. C. D.
Answer» Correct Answer - C

Discussion

Explore topic-wise InterviewSolutions in .

An electron is fired through a region of crossed electric and magnetic field (0.05 T) . The electric field is formed between two plates separated by a distance of 2 mm having a P.D. of 125 V . The speed of the electron isA. `12.5 xx 10^(6)` m/sB. `1250 ` K m/sC. 125 K m/sD. `1.25 xx 10^(7)` m/s

If the threshold wavelength for a certain metal is `2000Å`, then the work function of the metal isA. `6.2`JB. `6.2eV`C. `6.2MeV`D. `6.2Ev`

The number of photons required to give a definite energy W variesA. inversely as the frequencyB. directly as the frequencyC. independent of the frequencyD. inversely as the wavelength

The wavelength of an electron , moving with the velocity `3 xx 10^(3)` m/s , is nearly equal toA. `2xx10^(-12) `mB. `6 xx 10^(-13)` mC. `2.5 xx 10^(-7)` mD. `8 xx 10^(-10)`m

The dual nature of matter was predicted byA. EinsteinB. ComptonC. de BroglieD. Thomson

A quantum of light energy is calledA. protonB. photonC. electronD. neutron

The momentum of moving particle is p . The wavelength `lambda` of the associated matter wave will beA. h/pB. hpC. p/hD. p

The work function of a substance is `1.6 eV`. The longest wavelength of light that can produce photoemisson form the substance isA. 2900 ÅB. 3867 ÅC. 5800 ÅD. 7734 Å

In photoelectric effectA. light energy is converted into the heat energyB. light is converted into electric energyC. light energy is converted into the sound energyD. electric energy is converted into light energy

The rest mass of a photon of wavelength `lambda` isA. ZeroB. `h// c lambda`C. `h// lambda`D. `hc//lambda`

The momentum of a photon of wavelength `lambda` isA. `h lambda`B. `h//lambda`C. ` lambda//h `D. `h//c lambda`

The energy of a photon of wavelength `lambda` is given byA. `hc lambda`B. `h c//lambda`C. `lambda//hc `D. `h lambda//c`

The idea of the quantum nature of light has emerged in an attempt to explainA. radioactivityB. thermionic emissionC. interference of lightD. thermal radiations of a black body

A photon in motion has a massA. c/hvB. h/vC. hvD. `hv//c^(2)`

A metal surface is illuminated by the protons of energy 5 eV and 2.5 eV respectively . The ratio of their wavelength isA. `1 : 3`B. `1 : 4`C. `1 : 2`D. `2 :1`

The energy radiated from a source is in the form ofA. atomsB. photonsC. deuteronsD. electrons

The amount of energy radiated by a body depends uponA. the area of the surfaceB. the temperature of its surfaceC. the nature of its surfaceD. all of these

Photoelectric cell is a device in which the light energy is converted intoA. heat energyB. mechanical energyC. electric energyD. kinetic energy

The strength of the photoelectric current depends uponA. frequency of incident radiationB. intensity of incident radiationC. angle of incident radiationD. distance between anode and cathode

The maximum number of the photoelectrons , released in a photocell , is independent ofA. nature of the cathode surfaceB. frequency of the incident lightC. intensity of the radiationsD. whether of the atmosphere

The use of photoelectric cell in cinema depends upon the fact that the number of electrons produced is directly proportional toA. charge of electronsB. wavelength of lightC. intensity of lightD. all of these

The stopping potential for the photoelectrons , from a photocell , is proportionalA. directly on the intensity of incident lightB. inversely to the intensity of incident lightC. directly to the frequency of incident lightD. inversely to the frequency of incident light

In photoelectric cell ,the electrons leave the surface with maximum energy , which areA. just on the surfaceB. just below the surfaceC. 2 mm above the surfaceD. 2 mm below the surface

When an inert gas is filled in the place vacuum in a photo cell , thenA. photo current will decreaseB. photo current will increaseC. photo current remains the sameD. photo current does not depend upon the filled gas

Light of two different frequencies whose photons have energies 1eV and 2.5 eV respectively illuminate a metallic surface whose work function is 0.5 eV successively. Ratio of maximum kinetic energy of emitted electrons will be:A. `1:2`B. `1:1`C. `1:5`D. `1:4`

The photoelectrons emitted from a given cathode , on the incidence of a given monochromatic beam of light haveA. an energy spread with a lower limitB. an energy spread with an upper limitC. an energy spread with no sharp limitD. a definite energy only

Photoelectrons are emitted by a metal surface only whenA. the frequency of incident light exceeds a certain minimum valueB. the wavelength of the incident light exceeds a certain minimum valueC. the light is incident at an angle greater than the critical angleD. the metal is initially charged

If the kinetic energy of the particle is increased to `16` times its previous value , the percentage change in the de - Broglie wavelength of the particle isA. 25B. 75C. 60D. 50

Threshold wavelength for photoelectric effect on sodium is `5000 Å` . Its work function isA. `4 xx 10^(-19) J`B. `1 J`C. `2 xx 10^(-19)` JD. `3 xx 10^(-19)` J

Threshold wavelength for photoelectric effect on sodium is `5000 Å` . Its work function isA. 15 JB. `16 xx 10^(-14) J`C. `4 xx 10^(-19) J`D. `4 xx 10^(-18) J`

A metal has a threshold wavelength fo `6000 Å`. Calculate (i) threshold frequency (ii) work function. Will there be photoelectric emission or not ?

Monochromatic X-rays, when reflected from a crystal with lattice spacing `2.0 Å`, produce first order diffraction maximum at `theta=30^(@)`. What is the wavelength of X-rays ?

What voltage must be applied to an electron microscope to produce electrons of wavelength `0.4A`?

What is the energy of emitted photoelectrons is light of frequency `10^(16) Hz` is incident on a sodium target ? Work function of sodium is = 2.5 eV.

An electron moving at the speed of `10^(7)` m/s , enters a magnetic field of induction 0.1 T at right angle to the velocity of electron . The radius of circular path followed by the electron isA. 0.57 cmB. 5.7 cmC. 0.57 mmD. 0.27 mm

An electron experiences a force equal to its weight, when placed in an electric field. The intensity of the field will beA. `1.7 xx 10^(-11)` N/CB. `5 xx 10^(-11) ` N/CC. `17 xx 10^(-11)` N/CD. `50 xx 10^(-11)` N/C

For a certain metal `v = 2 v_(0)` and the electrons come out with a maximum velocity of `4 xx 10^(6)` m/s . If the value of ` v = 5 v_(0)` , then maximum velocity of the photoelectrons will beA. `8 xx 10^(5)` m/sB. `2 xx 10^(6)` m/sC. `8 xx 10^(6)` m/sD. `2 xx 10^(7)` m/s

The energy of incident radiation, which emits the electrons with a velocity of `2.5 xx 10^(6)` m/s and work function 1.8 e V , isA. `1.937` eVB. 2 e VC. 19.57 e VD. 20.1 eV

An electron of work function 1.4 eV is emitted with a velocity `5 xx 10^(6)` m/s . The wavelength of the incident radiation isA. `0.017` ÅB. 1.7 ÅC. 17 ÅD. 170 Å

Mutually perpendicular electric and magnetic fields are given by E = 1500 V/m and B = 0.04 T . Then velocity is given byA. 60 m/sB. `3.75 xx 10^(6)` m/sC. `3.75 xx 10^(4)` m/sD. `60 xx 10^(4)` m/s

When light of 2.5 eV falls on a metal surface, maximum kinetic energy of electron is T. If incident radiation of 4 eV falls on same metal surface, maximum kinetic energy of electrons is doubled. The work function of metal isA. 1 eVB. 4 e VC. 1.5 eVD. 0.5 eV

The radiations of 1 eV and 2.5 eV are incident on a metal having a work function of 0.5 eV . The ratio of their maximum velocities isA. `(1)/(2)`B. `(1)/(4)`C. `(2)/(5)`D. `sqrt((5)/(2))`

Which of the following graphs represents correctly the variations of `0.5 mv_("max")^(2)` with the intensity of incident radiations of a constant frequency ?A. B. C. D.