An electron of mass 9. 1 x 10\(^{-31}\) kg moves with a velocity of 4.2 x 10 ms\(^{-1}\) between the cathode and anode of an x-ray tube. Calculate the wavelength. (Take Planck’s constant h = 6.6 x 10\(^{-34}\) J S)
Explanation
P = mv = 9.1 x 10\(^{31}\) x 4.2 x 10\(^{-7}\)
= 9.1 x 4.2 x 10\(^{-24}\) Kgms\(^{-1}\)
\(\lambda = \frac{h}{p} = \frac{6.6 \times 10^{-34}}{9.1 \times 4.2 \times 10^{-24}}\)
= 1.73 x 10\(^{-11}\)m
or
\(\lambda = \frac{h}{mv} = \frac{6.6 \times 10^{-34}}{9.1 \times 10^{-31} \times 4.2 \times 10^7}\) = 1.73 x 10\(^{-11}\)