Question:

The wavelength associated with the electron moving in the first orbit of hydrogen atom with velocity \(2.2\times 10^6\,\text{m s}^{-1}\) (in nm) is
\((m_e=9.0\times 10^{-31}\,\text{kg},\; h=6.6\times 10^{-34}\,\text{Js})\)

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The de Broglie wavelength of a particle is given by \[ \lambda=\frac{h}{mv} \] A smaller mass or lower velocity results in a larger wavelength.
Updated On: Jun 22, 2026
  • \(0.66\)
  • \(0.33\)
  • \(0.22\)
  • \(0.44\)
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The Correct Option is B

Solution and Explanation

Step 1: Use de Broglie wavelength formula.
The wavelength associated with a moving particle is given by de Broglie relation: \[ \lambda=\frac{h}{mv} \] where \[ h=6.6\times 10^{-34}\,\text{Js} \] \[ m=9.0\times 10^{-31}\,\text{kg} \] \[ v=2.2\times 10^6\,\text{m s}^{-1} \]

Step 2: Substitute the given values.
\[ \lambda=\frac{6.6\times 10^{-34}} {(9.0\times 10^{-31})(2.2\times 10^6)} \] First calculate the denominator: \[ 9.0\times 2.2=19.8 \] and \[ 10^{-31}\times 10^6=10^{-25} \] Thus, \[ \lambda=\frac{6.6\times 10^{-34}} {19.8\times 10^{-25}} \] \[ \lambda=\frac{6.6}{19.8}\times 10^{-9} \] \[ \lambda=0.333\times 10^{-9}\,\text{m} \] \[ \lambda=3.33\times 10^{-10}\,\text{m} \]

Step 3: Convert metre into nanometre.
Since, \[ 1\,\text{nm}=10^{-9}\,\text{m} \] we get \[ \lambda=0.33\,\text{nm} \]

Step 4: Final conclusion.
Therefore, the wavelength associated with the electron is \[ \boxed{0.33\,\text{nm}} \]
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