$X$ and $Y$ are two metals. When burnt in air,$X$ forms only oxide while $Y$ forms oxide and nitride. The metals $X$ and $Y$ may be

$A$ concave mirror of focal length $f$ (in air) is immersed in water $(\mu = 4/3)$. The focal length of the mirror in water will be

Different conformations of the same molecule are called

$A$ point moves with uniform acceleration and $V_1, V_2$ and $V_3$ denote the average velocities in the three successive intervals of time $t_1, t_2$ and $t_3$. Which of the following relations is correct?

If $\alpha, \beta, \gamma$ are the roots of the equation $x^3+a x^2+b x+c=0$,then $\alpha^{-1}+\beta^{-1}+\gamma^{-1}$ is equal to

The length of the subtangent at any point $(x_1, y_1)$ on the curve $y=5^x$ is