A solution containing active cobalt $${^{60}_{27}}Co$$ having activity of $$0.8$$ $$\mu Ci$$ and decay constant $$\lambda $$ is injected in an animal's body. If $$1\,c{m^3}$$ of blood is drawn from the animal's body after $$10$$ hrs of injection, the activity found was $$300$$ decays per minute What is the volume of blood that is flowing in the body ? $$\left( {\,\,Ci = 3.7 \times {{10}^{10}}\,} \right.$$ decays per second and at $$t=10$$ hrs $$\left. {{e^{ - \lambda t}} = 0.84} \right)$$

The acceleration of an electron in the first orbit of the hydrogen atom (n = 1) is :

Imagine that a reactor converts all given mass into energy and that it operates at a power level of 10⁹ watt. The mass of the fuel consumed per hour in the reactor will be : (velocity of light, c is 3×10⁸ m/s)

According to Bohr’s theory, the time averaged magnetic field at the centre (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the n^th orbit is proportional to : (n = principal quantum number)