HC Verma: Concepts of Physics - Volume 2 Bohr's Model and Physics of the Atom Pages 384-386: Q31 Solution: A beam of monochromatic light of wavelength ejects…

QPages 384-386: Q31: HC Verma: Concepts of Physics - Volume 2 Bohr's Model and Physics of the Atom Pages 384-386: Q31 Solution: A beam of monochromatic light of wavelength ejects…

A beam of monochromatic light of wavelength

\lambda

ejects photoelectrons from a cesium surface

\Phi = 1.9 \text{ eV}

). These photoelectrons are made to collide with hydrogen atoms in ground state. Find the maximum value of

\lambda

for which a) hydrogen atoms may be ionized, b) hydrogen atoms may get excited from the ground state to the first excited state and c) the excited hydrogen atoms may emit visible light.

Step-by-Step Verified Solution

**Answer:** (a) __max for ionization = 91 nm. (b) __max for first excitation = 121.6 nm. (c) __max for visible light = 656 nm. **Step-by-Step Explanation:** (a) Ionization requires E � 13.6 eV. _ � 1240/13.6 = 91.2 nm. (b) First excitation requires E � 10.2 eV. _ � 1240/10.2 = 121.6 nm. (c) Visible light emission requires transition to n=2. The longest wavelength is H_ (656 nm), requiring excitation to n=3 (12.09 eV). _ � 1240/12.09 = 102.6 nm [citation:3].

QPages 384-386: Q31: HC Verma: Concepts of Physics - Volume 2 Bohr's Model and Physics of the Atom Pages 384-386: Q31 Solution: A beam of monochromatic light of wavelength ejects…

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