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})