Which of the following bonds are present in silicones?

$A$ 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

Two stones of masses $m$ and $3m$ are whirled in horizontal circles,the heavier one in a radius $\left(\frac{r}{3}\right)$ and the lighter one in a radius $r$. The tangential speed of the lighter stone is '$n$' times the value of the heavier stone. When the magnitude of the centripetal force becomes equal,the value of $n$ is:

Which disease is characterized by the appearance of dry,scaly lesions on various parts of the body such as the skin,nails,and scalp?

$A$ prism of refractive index $\sqrt{2}$ has a refracting angle of $60^{\circ}$. In order for a ray to suffer minimum deviation,it should be incident at an angle of.......$^{\circ}$.

Two cylinders $A$ and $B$ fitted with pistons contain equal number of moles of an ideal monoatomic gas at $400 ~K$. The piston of $A$ is free to move while that of $B$ is held fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in $A$ is $42 ~K$,the rise in temperature of the gas in $B$ is (in $~K$)