The bond energy of $Cl_2$,$Br_2$,and $I_2$ follows the order:

Which one of the following has the longest covalent bond distance?

The $rms$ value of the electric field of light coming from the Sun is $720\, N/C$. The average total energy density of the electromagnetic wave is

$A$ very small hole in an electric furnace is used for heating metals. The hole nearly acts as a black body. The area of the hole is $200 ~mm^2$. To keep a metal at $727^{\circ} C$,the heat energy flowing through this hole per second,in joules,is $\left(\sigma = 5.67 \times 10^{-8} ~W m^{-2} K^{-4}\right)$.

The function $f(x) = |x| + \frac{|x|}{x}$ is

The value of $\cos \frac{2 \pi}{15} \cos \frac{4 \pi}{15} \cos \frac{8 \pi}{15} \cos \frac{14 \pi}{15}$ is :