The major product of the following reaction is :

$A$ lens of power $+2 \text{ diopters}$ is placed in contact with a lens of power $-1 \text{ diopter}$. The combination will behave like:

The energy of a photon is equal to the kinetic energy of a proton. If $\lambda_1$ is the de-Broglie wavelength of a proton and $\lambda_2$ is the wavelength associated with the photon,and if the energy of the photon is $E$,then $(\lambda_1 / \lambda_2)$ is proportional to

Five point charges,each having magnitude $q$,are placed at the corners of a hexagon as shown in the figure. The net electric field at the centre $O$ is $\vec{E}$. To make the net electric field at $O$ equal to $6\vec{E}$,the charge to be placed on the remaining sixth corner should be: (in $q$)

$A$ convex lens is made up of three different materials as shown in the figure. For a point object placed on its axis,the number of images formed is:

The velocities of two particles $A$ and $B$ are $0.05 \ ms^{-1}$ and $0.02 \ ms^{-1}$ respectively. The mass of $B$ is five times the mass of $A$. The ratio of their de-Broglie's wavelength is