IISER 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
Cathode rays are projected pointing normal to the direction of electric field. Their path is
- (a)
straight line
- (b)
ellipse
- (c)
circle
- (d)
parabola
The specific charge of a proton is 9.6\(\times 10^{7}C \ kg^{-1}\). That for \(\alpha \) particle will be
- (a)
9.6\(\times 10^{7}C \ kg^{-1}\)
- (b)
4.8\(\times 10^{7}C \ kg^{-1}\)
- (c)
2.4\(\times 10^{7}C \ kg^{-1}\)
- (d)
38.4\(\times 10^{7}C \ kg^{-1}\)
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
A photon in motion has a mass equal to
- (a)
\(C/h\upsilon \)
- (b)
\(h/\lambda \)
- (c)
\(h\upsilon /c\)
- (d)
\(h\upsilon /c^{2}\)
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
The resistance of a discharge tube at a very low pressure is
- (a)
zero
- (b)
ohmic
- (c)
approaching infinity
- (d)
non-ohmic
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)
\(xe\over E\)
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
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
Dynamic mass of photon of wavelength \(\lambda \) is
- (a)
zero
- (b)
\(hc/\lambda \)
- (c)
\(h/c\lambda \)
- (d)
\(h/\lambda \)
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
The particle nature of radiation is confirmed by photo-electric effect because
- (a)
energy of photo-electron depends upon the intensity
- (b)
energy of photo-electron depends upon the frequency
- (c)
radiation creates electrons
- (d)
None of these
Photoelectric effect is an indirect evidence of
- (a)
wave theory of light
- (b)
quantum theory of light
- (c)
corpuscular theory of light
- (d)
electromagnetic wave theory of light
Which of the following phenomenon supports the quantum nature of light?
- (a)
interference
- (b)
diffraction
- (c)
polarisation
- (d)
Compton effect
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 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 dimensional formula for Planck's constant is
- (a)
\(MLT^{-2}\)
- (b)
\(ML^{2}T^{-3}\)
- (c)
\(ML^{2}T^{-1}\)
- (d)
\(ML^{0}T^{-3}\)
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 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 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
The maximum kinetic energy of photo electrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential in volts is
- (a)
2
- (b)
4
- (c)
6
- (d)
10
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)
\(\lambda ={4\pi R\over n}\)
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
When green light is incident on a certain metal surface electrons are emitted, but no electrons are emitted by yellow light. If red light is incident on the same metal surface them
- (a)
more energetic electrons will be emitted
- (b)
less energetic electrons will be emitted
- (c)
emission of electrons will depend on the intensity of light
- (d)
no electrons will be emitted
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)
\(4\times10^{15}\)
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