In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by:

The symbolic representation of four gates is shown as: 
   
Pick out which ones are for AND, NAND, and NOT gates, respectively.

A radioactive nucleus of mass M emits a photon of frequency $\nu$ and the nucleus will recoil. The recoil energy will be:

1.  $\frac{{\mathrm{h}}^2{\mathrm{\nu }}^2}{2{\mathrm{Mc}}^2}$

2.  zero

3.  $\frac{\mathrm{h\nu }}{\mathrm{c}\sqrt{2\mathrm{M}}}$

4.  $\frac{\mathrm{c}\sqrt{2\mathrm{M}}}{\mathrm{h\nu }}$

A particle moves in a circle of radius \(5\) cm with constant speed and time period \(0.2\pi\) s. The acceleration of the particle is:

The power obtained in a reactor using \(\mathrm{U}^{235}\) ${\mathrm{}}^{}$disintegration is \(1000~\text{kW}\). The mass decay of \(\mathrm{U}^{235}\) ${\mathrm{}}^{}$per hour is approximately equal to:
1. \(20~\mu\text{g}\)
2. \(40~\mu\text{g}\)
3. \(1~\mu\text{g}\)
4. \(10~\mu\text{g}\)

The half-life of a radioactive element X is 50 yrs. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1:15 in a sample of a given rock. The age of the rock was estimated to be:

1.  200 yr

2.  250 yr

3.  100 yr

4.  150 yr

A parallel plate condenser has a uniform electric field \(E\) (V/m) in the space between the plates. If the distance between the plates is \(d\) (m) and the area of each plate is \(A\) (m²), the energy (joule) stored in the condenser is:
1. \( \frac{1}{2}\varepsilon_0{E}^2 \)
2. \( \frac{{E}^2 {Ad}}{\varepsilon_0} \)
3. \( \frac{1}{2}\varepsilon_0 E^2 Ad \)
4. \(\varepsilon_0 EAd \)

If power dissipated in the \(9~\Omega\) resistor in the circuit shown is \(36\) W, the potential difference across the \(2~\Omega\) resistor will be: