Questions

Concave type of glasses are used in the headlights of the vehicles as the light from the bulb which is at focus will converges out and spreads and reflects back parallely.

When traveling in a vacuum, electronic waves from the electromagnetic spectrum all travel at the same speed. Velocity is speed with direction, so they would all travel at the same velocity, realtively speaking. But frequency and wavelength are quite different.

The given statement option A) is False regarding energy balance.
It should be "Inactive people use less energy so they should consume fewer calories."

Let the required number be 'X'

Condition 1 :  

$$\begin{gathered} XX = 2X \\ => 2X2 = X \\ => X = 12 \end{gathered}$$

Condition 2 :

$$\begin{gathered} X × X = X2 \\ => X = 12 \end{gathered}$$

Therefore, 12 is the number which becomes double when it is divided by itself and becomes half when it is multiplied by itself.

The highest of this peak is 1772 m.