What is the path difference for destructive interference?

The negation of $\sim s \vee (\sim r \wedge s)$ is equivalent to

In humans,which disorder is caused due to the absence of one of the $X$ chromosomes,i.e.,$45$ chromosomes with $XO$ genotype?

The transition from the state $n = 4$ to $n = 3$ in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition:

The metal ion present in vitamin $B_{12}$ is

The number of angular and radial nodes of $4d$ orbital respectively are