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Explain the observations made by Hertz and Lenard about the phenomenon of photoelectric
emission.
Concept: Particle Nature of Light
The number of photoelectrons emitted _______.
(A) varies inversely with frequency
(B) varies directly with frequency
(C) varies inversely with intensity
(D) varies directly with intensity
Concept: Particle Nature of Light
The momentum associated with the photon is given by_______.
(a) hv
(b) `"hv"/c`
(c) hE
(d) hλ
Concept: Particle Nature of Light
The work function for a metal surface is 2.2eV. If the light of wavelength 5000Å is incident on the surface of the metal, find the threshold frequency and incident frequency. Will there be an emission of photoelectrons or not? (c = 3 x 108 m/ s, 1eV = 1.6x10-19 J , h = 6.63 x 10-34 J.s.)
Concept: Einstein’s Equation - Particle Nature of Light
What is photoelectri effect ? Defin (i) Stopping potential (ii) Photoelectric work function.
Concept: Photoelectric Effect - Hertz’s Observations
The decay constant of radioactive substance is 4.33 x 10-4 per year. Calculate its half life period.
Concept: Law of Radioactive Decay
With the help of a neat labelled diagram, describe the Geiger- Marsden experiment
Concept: Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom
An electron is orbiting in 5th Bohr orbit. Calculate ionisation energy for this atom, if the ground state energy is -13.6 eV.
Concept: Bohr’s Model for Hydrogen Atom
Obtain an expression for the radius of Bohr orbit for H-atom.
Concept: Bohr’s Model for Hydrogen Atom
State Bohr’s third postulate for hydrogen (H2) atom. Derive Bohr’s formula for the wave number. Obtain expressions for longest and shortest wavelength of spectral lines in ultraviolet region for hydrogen atom
Concept: Bohr’s Model for Hydrogen Atom
Light of a certain wavelength has a wave number `barv` in vacuum. Its wave number in a medium of refractive index n is _______.
Concept: Wavelength of an Electron
Calculate the de Broglie wavelength of an electron moving with - of the speed of light in vacuum (Negelct relativistic effect)
(Planck's constant: h = 6.63 x 10-34 Js, Mass of electron : m = 9.11 x 10-28 g)
Concept: de-Broglie Relation
Derive an expression for the total energy of electron in ‘n' th Bohr orbit. Hence show that energy of the electron is inversely proportional to the square of principal quantum number. Also define binding energy.
Concept: Mass-energy and Nuclear Binding Energy >> Nuclear Binding Energy
The nuclei having same number of protons but different number of neutrons are called ___ .
(a) isobars
(b) a-particles
(c) isotopes
(d) y-particles
Concept: Hydrogen Spectrum
Describe the construction of photoelectric cell.
Concept: Wave Nature of Matter
Draw a neat labelled diagram for Davisson and Germer experiment, for diffraction of electron wave.
Concept: Davisson and Germer Experiment
Calculate the radius of second Bohr orbit in hydrogen atom from the given data.
Mass of electron = 9.1 x 10-31kg
Charge on the electron = 1.6 x 10-19 C
Planck’s constant = 6.63 x 10-34 J-s.
Permittivity of free space = 8.85 x 10-12 C2/Nm2
Concept: Bohr’s Model for Hydrogen Atom
In a photon-electron collision ______.
(A) only total energy is conserved.
(B) only total momentum is conserved.
(C) both total energy and total momentum are conserved.
(D) both total momentum and total energy are not conserved
Concept: Forms of Energy > Nuclear Energy >> Nuclear Fusion – Energy Generation in Stars
Find the frequency of revolution of an electron in Bohr’s 2nd orbit; if the radius and speed of electron in that orbit is 2.14 × 10-10 m and 1.09 × 106 m/s respectively. [π= 3.142]
Concept: Bohr’s Model for Hydrogen Atom
Draw a neat, labelled energy level diagram for H atom showing the transitions. Explain the series of spectral lines for H atom, whose fixed inner orbit numbers are 3 and 4 respectively.
Concept: Bohr’s Model for Hydrogen Atom
