According to Bohr's model of a hydrogen atom, the relation between the principal quantum number \(n\) and the radius of the stable orbit is:
1. \(r\propto\frac1n\)
2. \(r\propto n\)
3. \(r\propto\frac{1}{n^2}\)
4. \(r\propto n^2\)

An observer is approaching with velocity \(v\) towards a light source. If the velocity of light is \(c,\) then the velocity of light with respect to the observer will be:
1. \(c-v\)
2. \(c\)
3. \(c+v\)
4. \(\sqrt{1-v^2/c^2}\)

Magnetic field of the earth is H = 0. 3 g. A magnet vibrates 5 oscillations per min. then the depreciation required in the magnetic field of the earth of increased time period up to 10 oscillations per minute is:

1. 2.25 g

2. 0.6 g

3. 0.9 g

4. 0.12 g

Work function of a metal is \(5.2 \times 10^{-18}~\mathrm{J} \) then its threshold wavelength will be:
1. \(736.7~\mathrm{\mathring A}\) 
2.  \(760.7~\mathrm{\mathring A}\) 
3.  \(301~\mathrm{\mathring A}\) 
4.  \(378.4~\mathring A\)

Remaining quantity (in %) of radioactive element after 5 half-lives is:

1. 4.125%

2. 3.125%

3. 31.1%

4. 42.125%

An engine pumps up 100 kg of water through a height of 10 m in 5 s. Given that, the efficiency of an engine is 60%. If g = 10 ms^-2, the power of this engine is:

1. 3.3 kW

2. 0.33 kW

3. 0.033 kW

4. 33 kW

The angular amplitude of a simple pendulum is \(\theta^\circ.\) The maximum tension in its string will be:
1. \(mg(1-\theta_0)\)
2. \(mg(1+\theta_0)\) 
3. \(mg(1-\theta_0^2)\)
4. \(mg(1+\theta_0^2)\)

If the electric flux entering and leaving an enclosed surface respectively are \(\phi_1\) and \(\phi_2,\) the electric charge inside the surface will be:
1. \(\frac{\phi_2-\phi_1}{\varepsilon_0}\)
2. \(\frac{\phi_2+\phi_1}{\varepsilon_0}\)
3. \(\phi_2-\phi_1~\varepsilon_0\)
4. \(\varepsilon_0\phi_1+\phi_2\)

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of absolute temperature. The ratio \(\frac{C_P}{C_V}\) for the gas is:
1. \(\frac43\)
2.  \(2\)
3.  \(\frac53\)
4.  \(\frac32\)

Three point charges +q, -2q and +q are placed at points (x=O, y= a, z =O), (x=O, y=O, z=O) and (x = a, y = 0, z = 0), respectively. The magnitude and direction of the electric dipole moment vector of this charging assembly are: