In angiosperms,the functional megaspore develops into:

In Young's double slit experiment,the seventh maximum with wavelength ${\lambda _1}$ is at a distance $d_1$ from the central maxima,and the same maximum with wavelength ${\lambda _2}$ is at a distance $d_2$. Then the ratio $d_1/d_2$ is:

Which one of the following is an artificial sweetening agent?

Dimensions of a block are $1\,cm \times 1\,cm \times 100\,cm$. If the specific resistance of its material is $3 \times 10^{-7}\, \Omega \cdot m$, then the resistance between the opposite rectangular faces (the square ends) is:

When the angle of incidence is $60^{\circ}$ on the surface of a glass slab,it is found that the reflected ray is completely polarized. The velocity of light in glass is

The minimum force required to start pushing a body up a rough (frictional coefficient $\mu$) inclined plane is $F_1$,while the minimum force needed to prevent it from sliding down is $F_2$. If the inclined plane makes an angle $\theta$ with the horizontal such that $\tan \theta = 2 \mu$,then the ratio $\frac{F_1}{F_2}$ is: