The unit vector is given by $a\hat{i} + b\hat{j} + c\hat{k}$. If the values of $a$ and $b$ are $0.6$ and $0.8$ respectively,find the value of $c$.

The resultant of $\vec{A}$ and $\vec{B}$ makes an angle $\alpha$ with $\vec{A}$ and $\beta$ with $\vec{B}$. Which of the following is correct?

What is the wave number of the lowest energy transition associated with the Paschen series?

A spherical raindrop evaporates at a rate proportional to its surface area. The differential equation involving the rate of change of its radius $r$ with time $t$ is ... (where $k$ is a positive constant)

If a unit vector is represented by $\vec{U} = 0.9\hat{i} - 0.2\hat{j} + m\hat{k}$, then the value of $m$ is

Which of the following elements is doped to a fiber amplifier in an optical fiber communication system?