If the kinetic energy of a particle in motion is decreased by $36 \%$, the increase in de-Broglie wavelength of the particle is

An electron of mass $m$ with initial velocity $\mathbf{v}=v_0 \hat{\mathbf{i}}\left(v_0>0\right)$ enters in an electric field $\mathbf{E}=-E_0 \hat{\mathbf{i}}$ ( $E_0$ is constant $>0$ ) at $t=0$. If $\lambda$ is its de-Broglie wavelength initially, then the de-Broglie wavelength after time $t$ is

The longest wavelength of light that can initiate photo electric effect in the metal of work function 9 eV is

Energy required to remove an electron from aluminium surface is 4.2 eV . If light of wavelength $2000 \mathring{A}$ falls on the surface, the velocity of the fastest ejected electron the surface will be