\(d=\sqrt{2Rh}, d\propto \sqrt{h}\)
\(d'\propto \sqrt{1.21h} = 1.1h\)
Percentage change in d = 10%
So, the correct option is (B): 10%
For Line-of-Sight (LOS) communication, the range of communication is given by:
\(R = \sqrt{(2 \times h \times d)}\)
where h is the height of the tower and d is the distance to the horizon.
Let's assume that the original height of the tower is h and the original range of communication is R. If the height of the tower is increased by 21%, the new height of the tower is 1.21h. The new range of communication is:
\(R' = \sqrt{(2 \times 1.21h \times d)} = \sqrt{(1.21)} \times \sqrt{(2 \times h \times d)} = 1.1 \times R\)
So the percentage change in range is:
\(\frac{(1.1R - R)}{R}\times100% = 0.1R / R * 100% = 10%\)
Therefore, the percentage change in range when the height of the tower is increased by 21% is 10%.
Hence, the correct option is (B): 10%.
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,

Find the correct combination of A, B, C and D inputs which can cause the LED to glow. 
Identify the correct truth table of the given logic circuit. 

What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)
A system that describes the information exchange between two points is called the communication system. The transmission and reception process of information is called communication. The major elements of communication are such as:
The following are the examples of communication systems:
Turning on Signal specification or technology, the communication system is categorized as follows:
