The amplitude of $$15 \sin (1000 \pi \mathrm{t})$$ is modulated by $$10 \sin (4 \pi \mathrm{t})$$ signal. The amplitude modulated signal contains frequencies of

A. $$500 \mathrm{~Hz}$$

B. $$2 \mathrm{~Hz}$$

C. $$250 \mathrm{~Hz}$$

D. $$498 \mathrm{~Hz}$$

E. $$502 \mathrm{~Hz}$$

Choose the correct answer from the options given below:

In satellite communication, the uplink frequency band used is :

A transmitting antenna is kept on the surface of the earth. The minimum height of receiving antenna required to receive the signal in line of sight at $$4 \mathrm{~km}$$ distance from it is $$x \times 10^{-2} \mathrm{~m}$$. The value of $$x$$ is __________.

(Let, radius of earth $$\mathrm{R}=6400 \mathrm{~km}$$ )

A message signal of frequency $$3 ~\mathrm{kHz}$$ is used to modulate a carrier signal of frequency $$1.5 ~\mathrm{MHz}$$. The bandwidth of the amplitude modulated wave is