Question

What is the de Broglie wavelength of an electron of energy 180 eV?

(Mass of electron = 9 x 10^-31 kg and Planck's constant = 6.6 x 10^-34 Js.)

Options

• 0.5 Å

• 0.9 Å

• 1.3 Å

• 1.8 Å

Answer 1

0.9 Å

Explanation:

`"E" = 180  "eV"`

` = 180 xx 1.6 xx 10^-19`

` = 2.88 xx 10^-17 "J"`

`"now"  lambda = "h"/sqrt(2"mE")`

`therefore lambda = (6.6 xx 10^-34)/[2 xx 9 xx 10^-31 xx 2.88 xx 10^-17]^(1/2)`

`=(6.6 xx 10^-34)/(7.2 xx 10^-24)`

`= 0.916 xx 10^-10 `

`"m" = 0.9  "Å"`