NEET UG 2017 — Modern Physics

Radioactive material $A$ has decay constant $8\lambda$ and material $B$ has decay constant $\lambda$. Initially they have the same number of nuclei. After what time, the ratio of number of nuclei of material $A$ to that $B$ will be $\frac{1}{e}?$

The given electrical network is equivalent to 

The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature $T$ (Kelvin) and mass $m$ is:

The photoelectric threshold wavelength of silver is $3250\times {10}^{–10} m$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536\times {10}^{–10} m$ is:- $(Given h=4.14\times {10}^{-15} eV s and c=3\times {10}^{8} m{ s}^{-1})$

Which one of the following represents forward bias diode?

The ratio of wavelengths of the last line of the Balmer series and the last line of the Lyman series is_____.