Troposphere: 1. The lowest layer of the atmosphere (0–12 km). 2. Contains most of the Earth’s weather phenomena. 3. Temperature decreases with altitude.
Thermosphere: 1. Extends from approximately 80 km to 500 km above the surface. 2. Contains ionized particles and reflects radio waves. 3. Temperature increases with altitude due to solar radiation.

In the adjoining figure, $\triangle CAB$ is a right triangle, right angled at A and $AD \perp BC$. Prove that $\triangle ADB \sim \triangle CDA$. Further, if $BC = 10$ cm and $CD = 2$ cm, find the length of AD. 
In the adjoining figure, TP and TQ are tangents drawn to a circle with centre O. If $\angle OPQ = 15^\circ$ and $\angle PTQ = \theta$, then find the value of $\sin 2\theta$. 