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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).

(i) Eneryg of one photon

Substituting the values in eq. (1), we have

(ii) Kinetic energy of emission
= hv - hv₀ = 3.10 - 2.13 = 0.97 eV

(iii)

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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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