Rutherford’s $\alpha$-particle experiment showed that the atoms have
Proton
Nucleus
Neutron
Electrons
$X$-rays incident on a material
An electron having de-Broglie wavelength $\lambda$ is incident on a target in a X-ray tube. Cut-off wavelength of emitted $X$-ray is :
What is head-on collision ? For that tell the impact parameter.