The de-Broglie wavelength associated with an electron accelerated through a potential difference of $\frac{200}{3} \mathrm{~V}$ is nearly

The ratio of de-Broglie wavelengths associated with thermal neutrons at temperatures $127^{\circ} \mathrm{C}$ and $352^{\circ} \mathrm{C}$ is

A laser produces a beam of light of frequency $5 \times 10^{14}$ Hz with an output power of 33 mW . The average number of photons emitted by the laser per second is (Planck's constant $=6.6 \times 10^{-34} \mathrm{Js}$ )

If the de-Broglie wavelength of an electron is 2 nm , then its kinetic energy is nearly (Planck's constant $=6.6 \times 10^{-34} \mathrm{Js}$ and mass of electron $=9 \times 10^{-31} \mathrm{~kg}$ )