Question

The de-Broglie wavelength of an electron moving with a velocity of $1.5 \times 10^{8} m / s$ is equal to that of a photon. The ratio of kinetic energy of the electron to that of the photon $\left(c=3 \times 10^{8} m / s \right)$

• A. 2
• B. 4
• C. $\frac{1}{2}$
• D. $\frac{1}{4}$

Answer 1

Answer: (D)

$\frac{1}{4}$

Answer 2

The ratio of kinetic energy of the electron to that of the photon.
$=\frac{v}{2 c}$
$=\frac{1.5 \times 10^{8}}{2 \times 3 \times 10^{8}}=\frac{1}{4}$