An electric dipole will have minimum potential energy when it subtends an angle

$$\left[\begin{array}{l} \cos 0^{\circ}=1 \\ \sin 0^{\circ}=0 \end{array}\right]\left[\begin{array}{l} \cos 90^{\circ}=0 \\ \cos \pi=-1 \end{array}\right]$$

A particle is performing S.H.M. about its mean position with an amplitude ' $a$ ' and periodic time ' $T$ '. The speed of the particle when its displacement from mean position is $\frac{a}{3}$ will be

In case of photoelectric effect, the graph of measured stopping potential $\left(\mathrm{V}_0\right)$ against frequency ' $v$ ' of incident light is a straight line. The slope of this line multiplied by the charge of electron (e) gives

Critical angle of light passing from glass to air is minimum for wavelength of