The $P-P-P$ bond angle in white phosphorus is

Which one of the following frequencies of radiation (in $Hz$) has a wavelength of $600 \ nm$?

The major product of the following reaction is

For $|x| < 1$,the constant term in the expansion of $\frac{1}{(x-1)^2(x-2)}$ is

Which of the following halogens undergoes disproportionation in water?

If $e$ and $e^{\prime}$ are the eccentricities of the ellipse $5x^2 + 9y^2 = 45$ and the hyperbola $5x^2 - 4y^2 = 45$ respectively,then $ee^{\prime}$ is equal to