23415.Find the de–Broglie wavelength of an electron with kinetic energy of 120 eV.
112 pm
95 pm
124 pm
102 pm
23416.When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2 λ, the stopping potential is 4/V. The threshold wavelength for the metallic surface is
5/2 λ
3 λ
4 λ
5 λ
23417.The de Broglie wavelength of an electron accelerated to a potential of 400 V is approximately
0.03 nm
0.04 nm
0.12 nm
0.06 nm
23418.A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1/2 m away , the number of electrons emitted by photocathode would
increase by a factor of 4
decrease by a factor of 4
increase by a factor of 2
decrease by a factor of 2
23419.Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively, successively illuminate a metallic surface whose work function is 0.5 eV. Ratio of maximum speeds of emitted electrons will be
1 : 2
1 : 5
1 : 1
1 : 4
23420.An α–particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wb/m2. The de Broglie wavelength associated with the particle will be
10 Å
0.01 Å
1 Å
0.1 Å
23421.Statement–1 : When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is Kmax. When the ultraviolet light is replaced by X–rays, both V0 and Kmax increase.
Statement–2 : Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.
Statement–2 : Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.
Statement–1 is true, Statement–2 is false
Statement–1 is false, Statement–2 is true
Statement–1 is true, Statement–2 is true; Statement–2 is the correct explanation of Statement–1
Statement–1 is true, Statement–2 is true; Statement–2 is the not the correct explanation of Statement–1
23422.The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately:
540 nm
400 nm
310 nm
220 nm
23423.According to Einstein s photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal Vs the frequency, of the incident radiation gives a straight line whose slope:
depends on the nature of the metal used
depends on the intensity of the radiation
depends both on the intensity of the radiation and the metal used
is the same for all metals and independent of the intensity of the radiation
23424.Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is
+3 V
+4 V
–1 V
–3 V
23425.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 is
25
75
60
50
23426.Light of wavelength λA and λB falls on two identical metal plates A and B respectively. The maximum kinetic energy of photoelectrons in KA and KB respectively, then which one of the following relations is true ? (λA = 2 λB)
KA < KB/2
2 KA = KB
KA = 2 KB
KA > 2 KB
23427.If the momentum of an electron is changed by P, then the de Broglie wavelength associated with it changes by 0.5%. The initial momentum of electron will be
200 P
400 P
P/200
100 P
23428.The de–Broglie wavelength ‘λ’ of a particle
is proportional to mass
is proportional to impulse
is inversely proportional to impulse
does not depend on impulse
23429.A certain metallic surface is illuminated with monochromatic light of wavelength λ. The stopping potential for photo–electric current for this light is 3V0. If the same surface is illuminated with light of wavelength 2λ, the stopping potential is V0. The threshold wavelength for this surface for photoelectric effect is
6λ
4λ
λ/4
λ/6