The binding energy per nucleon of $^{209}_{83}Bi$ is _______ MeV.

[Take $m(^{209}_{83}Bi) = 208.980388\ \text{u}$, $m_p = 1.007825\ \text{u}$, $m_n = 1.008665\ \text{u}$, $1\ \text{u} = 931\ \text{MeV}/c^2$]

The equation of motion of a particle is given by $x = a \sin(50t + \pi/3)$ cm. The particle will come to rest at time $t_1$ and it will have zero acceleration at time $t_2$. The $t_1$ and $t_2$ respectively are ________.

In a Young's double slit experiment, the intensity at some point on the screen is found to be $\frac{3}{4}$ times of the maximum of the interference pattern. The path difference between the interfering waves at this point is $\frac{\lambda}{x}$ where $\lambda$ is wavelength of the incident light. The value of $x$ is _______.

Using Bohr’s model, calculate the ratio of the magnetic fields generated due to the motion of the electrons in the 2^nd and 4^th orbits of hydrogen atom ________.