If the radius of the first orbit of the $H$ atom is $a_0$, then the de Broglie wavelength of the electron in the third orbit will be ....... (in $\pi a_0$)

$A$ metal is irradiated with light of wavelength $660 \, nm$. Given that the work function of the metal is $1.0 \, eV$,the de Broglie wavelength of the ejected electron is close to

The wavelength of the electron emitted by a metal sheet of work function $4 \ eV$ when photons from $EMR$ of wavelength $124 \ nm$ strike the metal plate is ........... $nm$.

Which one of the following explains light both as a stream of particles and as wave motion?

The de-Broglie wavelength of a tennis ball of mass $60 \ g$ moving with a velocity of $10 \ ms^{-1}$ is approximately . . . . . . (Planck's constant $h = 6.63 \times 10^{-34} \ J \cdot s$).

The energy of separation of an electron in a $H$ atom in an excited state is $3.4 \ eV$. The de-Broglie wavelength (in $\mathring{A}$) associated with the above electron is,if the radius of the first orbit of the $H$ atom is $0.53 \ \mathring{A}$.