The Electrons in a Beam Are Moving At $18 \mathrm {~m} / \mathrm { s }$

Short Answer

The electrons in a beam are moving at $18 \mathrm {~m} / \mathrm { s }$ . ( $m _ { \text {electron } } = 9.11 \times 10 ^ { - 31 } \mathrm {~kg} , h = 6.626 \times$ $10 ^ { - 34 } \mathrm {~J} \cdot \mathrm { s }$ )
(a) What is its de Broglie wavelength these electrons?
(b) If the electron beam falls normally on a diffraction grating, what would have to be the spacing between slits in the grating to give a first-order maximum at an angle of $30 ^ { \circ }$ with the normal to the grating?