$A$ certain radioactive substance reduces to $25\%$ of its initial value in $16$ days. Its half-life is ........ $days$.

An ideal coil of $10 \, H$ is connected in series with a resistance of $5 \, \Omega$ and a battery of $5 \, V$. $2 \, s$ after the connection is made,the current flowing (in ampere) in the circuit is:

$Fe$ is made passive by

$A$ light ray of wavelength $\lambda$ is passing through a pinhole of diameter $D$ and the effect is observed on a screen placed at a distance $L$ from the pinhole. The approximations of geometrical optics are applicable,if

$\int_0^{2 \pi} \sin^6 x \cos^5 x \, dx$ is equal to

Given below are two statements regarding silent heart attack.
Statement $I$: This type of heart attack shows symptoms like chest pain and shortness of breath.
Statement $II$: In this type of heart attack,usually person shows very mild symptoms and thus it is ignored.
In the light of above two statements,choose the correct answer from options given below.