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Structure of Atom

Short Answer Type

131.

What do you mean by absorption spectra?

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Long Answer Type

132. Explain in brief hydrogen spectra.

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133.

Describe briefly Planck's Quantum Theory.

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134.

Explain briefly the photoelectric effect.

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135.

A photon of wavelength 4 x 10^-7 m strikes on metal surface, the work function of the metal being 2.13 eV. Calculate: (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron (1 eV = 1.6020 10^-19J).

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Short Answer Type

136. The threshold frequency v₀ for a metal is 7.0 X 10¹⁴s^-1. Calculate the kinetic energy of an electron emitted when radiation of frequency v = 1.0 X 10¹⁵ s^-1 hits the metal.

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137. Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate the threshold frequency (v₀) and the work function (W₀) of the metal.

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Long Answer Type

138.

The work function for caesium atom is 1.9 eV. Calculate: (a) the threshold wavelength and (b) the threshold frequency of radiation. If the caesium element is irradiated with a wavelength 500 nm, calculate the kinetic energy and velocity of the ejected photoelectron.

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139. The ejection of the photoelectron from the silver metal in the photoelectric effect experiment can be stopped by applying the voltage of 0.35 V when the radiation 256.7 nm is used. Calculate the work function for silver metal.

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Short Answer Type

140. Describe applications of Quantum theory.

Application of Quantum theory:
(i) In 1905, Einstein applied this theory to explain the photoelectric effect.
(ii) In 1913, N. Bohr used this theory to explain the structure of atoms and explain hydrogen spectra.
(iii) In 1922, this theory was used to explain Compton effect.

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