The endosperm in angiosperms develops from

Find the length of the intercept cut by the pair of lines $2x^2+4xy-4y^2-6x-8y+7=0$ on the $Y$-axis.

$A$ short magnetic needle is pivoted in a uniform magnetic field of induction $1 ~T$. Now,simultaneously another magnetic field of induction $\sqrt{3} ~T$ is applied at right angles to the first field; the needle deflects through an angle $\theta$ whose value is (in $^{\circ}$)

Blister copper is refined by stirring molten impure metal with green logs of wood because such a wood liberates hydrocarbon gases (like $CH_4$). This process $X$ is called . . . . . . and the metal contains impurities of $Y$ is . . . . . . .

$A$ person is observing a bacteria through a compound microscope. For better observation and to improve its resolving power,he should:

$A$ photon collides with a stationary hydrogen atom in the ground state inelastically. The energy of the colliding photon is $10.2 \, eV$. After a time interval of the order of a microsecond,another photon collides with the same hydrogen atom inelastically with an energy of $15 \, eV$. What will be observed by the detector?