Nicotine acts as a stimulant because it mimics the effect of

If $n_1, n_2$,and $n_3$ are the fundamental frequencies of three segments into which a string is divided,then the original fundamental frequency $n$ of the string is given by

If $\alpha, \beta, \gamma$ are the roots of $x^3+2x^2-3x-1=0$,then $\alpha^{-2}+\beta^{-2}+\gamma^{-2}=$

Many ionic crystals dissolve in water because

In Earthworm,the dorsal wall of the intestine from the $26^{th}$ segment to the $95^{th}$ segment forms a median internal fold called:

$A$ Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is