Which gas is evolved when potassium ferrocyanide is heated with concentrated $H_2SO_4$?

Vitamin $B_{12}$ contains which of the following metals?

$A$ ray of light of intensity $I$ is incident on a parallel glass slab at point $A$ as shown in the diagram. It undergoes partial reflection and refraction. At each reflection, $25\%$ of incident energy is reflected. The rays $AB$ and $A'B'$ undergo interference. The ratio of $I_{max}$ and $I_{min}$ is (in $: 1$)

The energy band diagrams for three semiconductor samples of silicon are as shown. We can then assert that

In which method is recombinant $DNA$ directly injected into the nucleus of an animal cell?

If $f(t) = \int_{-t}^t \frac{e^{-|x|}}{2} dx$,then $\lim_{t \rightarrow \infty} f(t)$ is equal to: