Question

The maximum speed of moving electron having its de-broglie wavelength in visible range is:
(Given visible range $400nm-700nm$)(Take $h=6.6\times {10}^{-34}J-s$)

• A. $1.1\times {10}^{3}m/s$
• B. $1.8\times {10}^{4}m/s$
• C. $1.1\times {10}^{4}m/s$
• D. $1.8\times {10}^{3}m/s$

Answer 1

The correct option is D $1.8\times {10}^{3}m/s$

Momentum of electron $=\frac{h}{\lambda }$

$m_{e}V=\frac{h}{\lambda }$

$V=\frac{h}{m_e\lambda }$ ($\lambda$ should be minimum)

$2=400nm$

$=\frac{6.6\times {10}^{-34}}{9.1\times {10}^{-31}\times 400\times {10}^{-9}}$

$=1.8\times {10}^{3}m/s$