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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.

We know
Energy of the incident radiation = Work function + KE of photoelectron
Work function = Energy of the incident
radiation - KE of photoelectron ..(1).

Now energy of the incident radiation (E) = hv
   ..(2)

Substituting the values in eq. (2), we have

Energy of incident radiation

The potential applied gives the kinetic energy to the electron.
Hence, the kinetic energy of the electron = 4.4 eV.
Substituting the values in eq. (1), we have
Work function = 4.83 eV - 0.35 eV
= 4.48 eV

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Short Answer Type

140. Describe applications of Quantum theory.

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