# Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 4

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Q: 9. A photon of wavelength the work function of the metal being Calculate

(i) The energy of the photon (eV)

(ii) The kinetic energy of the emission

(iii) The velocity of the photoelectron (1 eV=).

Answer:

(i) Energy (E) of a photon =

Where,

Wavelength of photon

Substituting the values in the given expression of E:

Hence, the energy of the photon is.

(ii) The kinetic energy of emission is given by

Hence, the kinetic energy of emission is 0.97 eV.

(iii) The velocity of a photoelectron () can be calculated by the expression,

Where, () is the kinetic energy of emission in joules and ‘m’ is the mass of the photoelectron. Substituting the value in the given expression of v:

Hence, the velocity of the photoelectron is

Q: 10. Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize the sodium atom. Calculate the ionization energy of sodium in

Answer:

Energy of Sodium (E)

Q: 11. A watt bulb emits monochromatic yellow light of wavelength of Calculate the rate of emission of quanta per second.

Answer:

Power of bulb,

Energy of one photon,

Substituting the values in the given expression of E:

Rate of emission of quanta per second