Physics - Electrons and Protons
Exam Duration: 45 Mins Total Questions : 30
An electron is projected pointing in the same direction of electric and magnetic fields. Then
- (a)
the electron turns to right
- (b)
the electron turns to right
- (c)
the electron continues to move in the same direction but with less velocity
- (d)
the electron continues to move in the same direction but with increased velocity
Energy of an electron can be increased by
- (a)
making them fall from a great height
- (b)
moving them through an electric potential
- (c)
passing them through lead block
- (d)
passing them through high magnetic field
A photon in motion has a mass equal to
- (a)
\(C/h\upsilon \)
- (b)
\(h/\lambda \)
- (c)
\(h\upsilon /c\)
- (d)
\(h\upsilon /c^{2}\)
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 a dischange tube at 0.02 mm, there is formation of
- (a)
Faraday's dark space
- (b)
Crooke's dark space
- (c)
Both spaces partly
- (d)
Crooke's dark space with glow near the electrodes
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
In positive ray tube the pressure is of the order of
- (a)
\(10^{-7}\) cm of Hg
- (b)
\(10^{-3}\) cm of Hg
- (c)
0.1 cm of Hg
- (d)
1 cm of Hg
In a mass spectrograph an ion X of mass number 24 and charge +e and another Y of mass number 22 and charge +2e enter perpendicular to the field with same velocity. The ratio of the radii of their circular paths in the field will be
- (a)
24/11
- (b)
2 : 1
- (c)
11/2
- (d)
1 : 2
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
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
The distance between the two places of a cathode-ray oscilloscope is 1 cm and potential difference between them is 1200 volt. If an electron of energy 2000 eV enters at right angles to the field, what will be its enters at right angles to the field, what will be its deflection if the plate be 1.5 cm long ?
- (a)
0.34 cm
- (b)
0.34 cm
- (c)
3.4 cm
- (d)
34 cm
Energy of a photon is
- (a)
\(hc/\lambda \)
- (b)
\(hc\overline{v}\)
- (c)
\(mc^{2}\)
- (d)
all of the above
Photoelectric effect reveals
- (a)
the wave nature of radiation
- (b)
the particle nature of radiation
- (c)
both wave as well as particle nature of radiation
- (d)
None of these
Radition include energy travelling in the form of
- (a)
waves only
- (b)
particles only
- (c)
both waves and particles
- (d)
quanta of energy
The work function of a photoelectric material is 3.3eV. Its threshold frequency will be
- (a)
\(8\times10^{14}Hz\)
- (b)
\(5\times10^{33}Hz\)
- (c)
\(8\times10^{10}Hz\)
- (d)
\(4\times10^{11}Hz\)
When a certain metallic surface is illuminated with monochromatic light of wavelength \(\lambda \), the stopping potential for photo-electric current is 3V. When the same surface is illuminated with light of wavelength 2\(\lambda \), the stopping potential is \(V_{0}\). The threshold wavelength for this surface for photoelectric effect is
- (a)
6\(\lambda \)
- (b)
4\(\lambda \)
- (c)
\(\lambda \)/4
- (d)
8\(\lambda \)
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
Energy conversion in a photoelectric cell takes places from
- (a)
chemical to electrical
- (b)
magnetic to electrical
- (c)
optical to electrical
- (d)
mechanical to electrical
Photoelectric effect is based on the law of conservation of
- (a)
energy
- (b)
liner mass
- (c)
linear momentum
- (d)
angular momentum
Light of wavelength 4000 \(\mathring { A } \) is incident on a metal plate whose work function is 2.eV. What is the maximum kinetic energy of the emitted photoelectrons ?
- (a)
2.0 eV
- (b)
1.5 eV
- (c)
1.1 eV
- (d)
0.5 eV
In a photoelectric experiment, the stopping potential \(V_{s}\) is plotted against the frequancy \(\upsilon \), of the incident light. The resulting curve is a straight line which makes an angle \(\theta \) with the \(\upsilon \)-axis. Then tan \(\theta \) is equal to
- (a)
h/e
- (b)
e/h
- (c)
\(-\phi \)/e
- (d)
\(eh/\phi \)
The de Broglic equation states the
- (a)
particle nature
- (b)
wave nature
- (c)
dual nature
- (d)
None of these
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
The photoelectric effect from a metal surface begins at a frequency of \(6\times10^{14}\) Hz. The photoelectrons are fully stopped by a retarding potential of 3 V. The work function for this metal is
- (a)
1.2 eV
- (b)
0.8 eV
- (c)
3.2 eV
- (d)
2.5 eV
The energy of incident photon is 11.387 eV while the energy of scattered photon is 9.128 ev. Then the kinetic energy of recoil electron is
- (a)
2.255 eV
- (b)
less than 2.255 eV
- (c)
more than 2.255 eV
- (d)
20.515 eV
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)
\(180^{o}\)
An ionised gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction, then
- (a)
positive ions deflect toward +y direction and negative ions towards -y direction
- (b)
all ions deflect towards +y direction
- (c)
all ions deflect towards -y direction
- (d)
positive ions deflect toward -y direction and negative ions towards +y direction
The potential difference applied to an X-ray tube is 5 kV and the current through it is 3.2 mA. Then, the number of electrons striking the target per secound is
- (a)
\(2\times10^{16}\)
- (b)
\(5\times10^{16}\)
- (c)
\(1\times10^{17}\)
- (d)
\(4\times10^{15}\)