Two charges $q_1$ and $q_2$ are placed $30\,cm$ apart,as shown in the figure. $A$ third charge $q_3$ is moved along the arc of a circle of radius $40\,cm$ from $C$ to $D$. The change in the potential energy of the system is $\frac{q_3}{4\pi \epsilon_0}k$,where $k$ is:

Find the oxidation state of sodium in $Na_{2}O_{2}$.

$A$ neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is

Energy levels $A, B, C$ of a certain atom correspond to increasing values of energy, i.e., $E_A < E_B < E_C$. If $\lambda_1, \lambda_2, \lambda_3$ are the wavelengths of radiation corresponding to the transitions $C \to B$, $B \to A$, and $C \to A$ respectively, which of the following relations is correct?

In a biprism experiment,if the $5^{\text{th}}$ bright band with wavelength $\lambda_1$ coincides with the $6^{\text{th}}$ dark band with wavelength $\lambda_2$,then the ratio $\left(\frac{\lambda_2}{\lambda_1}\right)$ is:

Which pyrimidine bases are present in $DNA$?