A plate of refractive index 1.6 is introduced in the path of light from one of the slits in Young's double slit experiment then

The viscous force between two liquid layers is

In the given reaction

$${ }_z \mathrm{X}^A \rightarrow{ }_{z+1} \mathrm{Y}^A \rightarrow{ }_{z-1} \mathrm{~K}^{A-4} \rightarrow{ }_{z-1} \mathrm{~K}^{\mathrm{A}-4}$$

radioactive radiations are emitted in the sequence

Two point charges $+q_1$ and $q_2$ repel each other with a force of $100 \mathrm{~N} . q_1$ is increased by $10 \%$ and $q_2$ is decreased by $10 \%$. If they are kept at their original positions the change in the force of repulsion between them is