The value of $\cos 15^{\circ} \cos 7.5^{\circ} \sin 7.5^{\circ}$ is

Nicotine acts as a stimulant because it mimics the effect of

If the transverse and conjugate axes of a hyperbola are equal,then its eccentricity is

The total number of nitrogenous bases in the human genome is estimated to be about:

Two polaroids are placed in the path of an unpolarized beam of intensity $I_0$ such that no light is emitted from the second polaroid. If a third polaroid,whose polarization axis makes an angle $\theta$ with the polarization axis of the first polaroid,is placed between these polaroids,then the intensity of light emerging from the last polaroid will be

The packing efficiency of the two-dimensional square unit cell shown below is ........... $ \% $