Question
If an electron is accelerated through a potential difference 150 volt, its de-Broglie wavelength is:
A.
$$1\mathop {\text{A}}\limits^ \circ $$
B.
$$100\mathop {\text{A}}\limits^ \circ $$
C.
$$5000\mathop {\text{A}}\limits^ \circ $$
D.
$$90000\mathop {\text{A}}\limits^ \circ $$
Answer :
$$1\mathop {\text{A}}\limits^ \circ $$
Solution :
$$\eqalign{
& \lambda = \frac{h}{{\sqrt {2meV} }} = {\left( {\frac{{150}}{V}} \right)^{\frac{1}{2}}}\mathop {\text{A}}\limits^ \circ \cr
& = {\left( {\frac{{150}}{{150}}} \right)^{\frac{1}{2}}}\mathop {\text{A}}\limits^ \circ \cr
& = 1\mathop {\text{A}}\limits^ \circ \cr} $$