Let Mass of the electron is 9.1 × 10⁻³¹ kg.
K = 2.8 × 10⁻²³ J.
Since,
K = 1/2 × m × v²
⇒ 2.8 × 10⁻²³ = 1/2 × 9.1 × 10⁻³¹ × v²
⇒ v² = 0.615 × 10⁸
∴ v = 0.78 × 10⁴
Using the Formula,
λ = h/mv
⇒ λ = 6.62 × 10⁻³⁴/(9.1 × 10⁻³¹ × 0.78 × 10⁴)
∴ λ = 0.93 × 10⁻⁷ m.
Hence, the de-broglie wavelength of the Electron is 0.93 × 10⁻⁷ m