When Sunita, a class XII student came to know that her parents are planning to rent out the top floor of their house to a mobile company, she protested. She tried hard to convince her parents that this move would be a health hazard. Ultimately, her parents agreed.
(i) In what way can the setting up of transmission tower by a mobile company in a residential colony prove to be injurious to health?
(ii) By objecting to this move of her parents, what value did Sunita display?
(iii) Estimate the range of em waves which can be transmitted by the antenna of height 20 m (Given radius
of earth = 6400 km).

Explanation

(i) Transmission towers in a residential colony are potential health hazards. Some links have been establised
between radiations from cell phone towers and brain cancer. Further, these high structure can attract and
confuse birds. Millions of birds are killed near communication towers every year, raising health concerns.
(ii) By objecting to this move, Sunita displayed the practival use of the knowledge acquired by her, and also
her concern for the health of community all around.
(iii) Here, `h = 20 m, R = 6400 km = 6.4 xx 10^6m`
Range `= sqrt(2hR) = sqrt(2 xx 20 xx 6.4 xx 10^6) = 16 xx 10^3 m = 16 km`.