In Example $31-13,$ the author calculates the wave length for the K $$X$-$ray line emitted when electrons

hit a molybdenum target. $$What would happen to that value of the K $$wavelength is the energy of those incoming electrons had been doubled?

$1.$

It would go up by factor of $4.$

$2.$

It would go up by factor of $2.$

$3.$

It would not change.

$4.$

It would go down by a factor of $2.$

$5.$

It would go down by a factor of $4.$