JEE Main Physics - Electrons and Protons
Exam Duration: 60 Mins Total Questions : 30
Strong argument for the particle nature of cathode rays is to
- (a)
Produce fluorescence
- (b)
travel throught vacuum
- (c)
get deflection by electric and magnetic fields
- (d)
cast shadow
The specific charge of electron is
- (a)
\(1.6\times10^{-19}C\)
- (b)
\(9.1 \times10^{-31}kg\)
- (c)
\(1.76\times10^{11}C kg^{-1}\)
- (d)
\(5.7\times10^{-12}kg C^{-1}\)
A proton moving with velocity \(\vartheta \) is acted upon by electric field E and magnetic filed B. The proton will move undeflected if
- (a)
E is perpendicular to B
- (b)
E is parallel to \(\vartheta \) and perpendicular to B
- (c)
E, B and \(\vartheta \) are mutually perpendicular and \(\vartheta ={E\over B}\)
- (d)
E and B both are parallel to \(\vartheta \).
The path of moving electron is a parabola if electron has
- (a)
no initial velocity in a direction different from that of an electric field
- (b)
an initial velocity perpendicular to direction of an electric field
- (c)
Both (a) and (b) are true
- (d)
Both (a) and (b) are not true
The momentum of a photon of wavelength \(\lambda \) is
- (a)
\(h/\lambda \)
- (b)
\(h\upsilon /c^{2}\)
- (c)
\(h??\upsilon /c\)
- (d)
zero
Which one of the following statements about photon is NOT CORRECT ?
- (a)
Photons exert no pressure.
- (b)
Photon's energy is \(h\upsilon \).
- (c)
Photon's momentum is \(h\upsilon /c\).
- (d)
Photon's rest mass is zero.
The energy of photons in a beam whose wavelength is \(6.12 \times 10^{-15}\)cm is
- (a)
1 eV
- (b)
0.01 eV
- (c)
2.0 eV
- (d)
0.02 eV
In cathode ray tube for the determination of \(e\over m\) of electrons, the potential difference is suddenly increased so that the electrons begin to move with velocity close to the velocity of light. The effect of \(e\over m\).
- (a)
increases
- (b)
decreases
- (c)
remains same
- (d)
may either increase or decrease
A proton, a deutron and an \(\alpha \)- particle have same kinetic energies. Their velocities are in the ratio of
- (a)
\(1 : \sqrt2 : 1\)
- (b)
\(1 : 1 : \sqrt2\)
- (c)
\(\sqrt2 : 1 : 1\)
- (d)
\(1 : {1\over\sqrt2} : 1\)
An electron beam at rest is accelerated in a uniform electric field of strength E. The kinetic energy attained by it as it travels through a distance x is
- (a)
\(x\over E_{e}\)
- (b)
\(x Ee\)
- (c)
\(Ee\over x\)
- (d)
\(xe\over E\)
In Milikan's oil drop method, an oil drop having a charge 'ne' is held stationary by applying a potential difference of 400 V between two parallel plates. If the size of the drop is doubled without changing the charge, the potential difference required to keep it stationary is
- (a)
800 V
- (b)
1600 V
- (c)
3200 V
- (d)
200 V
An electron beam passes through a magnetic field of 2 mT and electrostatic field of \(3\times10^{-14}Vm^{-1}\) at right angles to it. If its specific charge is \(1.75 \times10^{11}C \ kg^{-1}\) and there is no deflection when both fields are acting, the radius of path of electron is
- (a)
0.43 cm
- (b)
4.3 cm
- (c)
0.43 m
- (d)
4.3 m
A current in an electron beam of a cathode ray tube is 4.8 mA. If an accelerating voltage is 2000 V, then the number of electrons striking the screen each second is (charge on electron = \(1.6 \ \times \ 10^{-19} \ C\))
- (a)
\(3 \times 10^{16}\) and kinetic energy, \(E_{k}\), of each electron is \(3.2 \times10^{-16}J\)
- (b)
\(6 \times 10^{6}\) and \(E_{k}\) is \(3.2 \times10^{-16}J\)
- (c)
\(3 \times 10^{18}\) and \(E_{k}\) is \(1.6 \times10^{-14}J\)
- (d)
None of the above
In CRO, the focussing of beam on the screen is obtained by
- (a)
magnetic field
- (b)
electric field
- (c)
either (b) or (c)
- (d)
both (a) and (b)
In Thomson's experiment, if the ratio E/B is less than velocity \(\vartheta \) of electron, then electron will more
- (a)
to a sport below the position of undeflected spot
- (b)
to a sport above the position of undeflected spot
- (c)
to the position of the undeflected spot
- (d)
towards the wall of the tube and will not reach the screen
When a monochromatic point-source of light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are respectively 0.6 volt and 18.0 mA. If same source is placed 0.6 m away from the photoelectric cell, then
- (a)
the stopping potential will be 0.2 volt
- (b)
the stopping potential will be 0.6 volt
- (c)
the saturation current will be 2.0 mA
- (d)
Both (b) and (c) are true
Energy of a photon is
- (a)
\(hc/\lambda \)
- (b)
\(hc\overline{v}\)
- (c)
\(mc^{2}\)
- (d)
all of the above
Diffraction of electron confirms that
- (a)
particles behave like waves
- (b)
particles have independent character
- (c)
waves show particle properties
- (d)
None of the above
The shortest wavelenght of X-ray emitted from an X-ray tube depends on
- (a)
the current in the tube
- (b)
the voltage applied to the tube
- (c)
the nature of the gas in the tube
- (d)
the atomic number of the target material
The work function of sodium is 2.3 eV. Sodium will NOT show photoelectric effect with which of the following colours ?
- (a)
Violet
- (b)
Blue
- (c)
Ultraviolet
- (d)
Yellow
In Millikan oil drop experiment a drop of charge Q and radius r is kept constant between two places of potential difference of 800 volt. Then charge on other drop of radius 2r which is kept constant with a potential difference of 3200 volt is
- (a)
Q/2
- (b)
2Q
- (c)
4Q
- (d)
Q/4
A light of inrensity \(I_{0}\) passes through a material of thickness d. The resultant intensity is
- (a)
\(I=I_{0}(1-e^{-\lambda d})\)
- (b)
\(I=I_{0}e^{-\lambda d}\)
- (c)
\(I=I_{0}e^{\lambda d}\)
- (d)
\(I=I_{0}(1-e^{-d/h})\)
Photoelectrons are ejected from a metal surface of work fuction 1.7 eV with light of energy 2.3 eV. Stopping potential needed to stop the photoelectrons is
- (a)
1.7 V
- (b)
4.0 V
- (c)
0.3 V
- (d)
0.6 V
Light of wavelength 2000 \(\mathring { A } \) falls on aluminium surface. In aluminium 4.2 eV are requried to remove an eletron.
A. Kinetic energy of the fastest emitted photoelectrons is 2. eV
B. Kinetic energy of the slowest emitted photoelectrons is 2 eV
C. Stopping potential for aluminium is 2 V
D. Cutt off wavelength for aluminium is 3000 \(\mathring { A } \)
Mark :
- (a)
If A is correct only
- (b)
if B is correct only
- (c)
if A and C correct only
- (d)
if A, C and D are correct only
The wavelength of incident light falling on a photosensitive surface is changed from 2000 \(\mathring { A } \) to 2100 \(\mathring { A } \). The corresponding change in stopping potential is
- (a)
0.03 V
- (b)
0.3 V
- (c)
3 V
- (d)
3.3 V
Maximum compton shift is independent of
- (a)
frequency of incident radiation
- (b)
material of target
- (c)
angle of scattering
- (d)
All of the above
The de Brogile wavelength \(\lambda \) of an electron in the \(n^{th}\) Bohr orbit is related to the radius R of the orbit as
- (a)
\(\lambda ={\pi R\over n}\)
- (b)
\(\lambda ={3\pi R\over 2n}\)
- (c)
\(\lambda ={2\pi R\over n}\)
- (d)
\(\lambda ={4\pi R\over n}\)
In Compton effect the value of Compton's shift is maximum for the photon scattering angle of
- (a)
\(0^{o}\)
- (b)
\(45^{o}\)
- (c)
\(90^{o}\)
- (d)
\(180^{o}\)
Graph of maximum kinetic energy of the photo-electrons against \(\upsilon \), the frequency of the incident radiation on the metal, is a straight line of slope equal to
- (a)
work function
- (b)
stopping potential
- (c)
h/e
- (d)
h
Particle nature and wave nature of electrons and electromagnetic waves be shown by which of the following statements:
- (a)
Electrons having small mass, deflected by the metal sheet
- (b)
X-ray diffracted, reflected by thick metal sheet
- (c)
Light refracted and diffracted
- (d)
Electron microscopy and photoelectricity