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

Two full turns of the circular scale of a screw gauge cover a distance of $1\,mm$ on the main scale. The total number of divisions on the circular scale is $50$. Further,it is found that the screw gauge has a zero error of $+0.03\,mm$. While measuring the diameter of a thin wire,a student notes the main scale reading of $3\,mm$ and the number of the circular scale division in line with the main scale is $35$. The diameter of the wire is .......... $mm$.

Identify the correct decreasing order of the following with respect to altitude from the atmosphere:
$I$. Troposphere
$II$. Mesosphere
$III$. Thermosphere

$A$ point charge $q$ is surrounded symmetrically by six identical charges $q$ at a distance $r$ as shown in the figure. How much work is done by the forces of electrostatic repulsion when the point charge $q$ at the centre is moved to infinity?

Which of the following organisms is not correctly matched with its taxonomic category?

When did $R.H. Whittaker$ propose the five-kingdom classification system?