JEE MAIN - Physics (2003 - No. 47)
A tuning fork of known frequency $$256$$ $$Hz$$ makes $$5$$ beats per second with the vibrating string of a piano. The beat frequency decreases to $$2$$ beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was
$$256 + 2Hz$$
$$256 - 2Hz$$
$$256 - 5Hz$$
$$256 + 5Hz$$
ব্যাখ্যা
A tuning fork of frequency $$256$$ $$Hz$$ makes $$5$$ beats/ second with the vibrating string of a piano. Therefore the frequency of the vibrating string of piano is $$\left( {256 \pm 5} \right)$$ $$Hz$$ ie either $$261$$$$Hz$$ or $$251$$ $$Hz.$$ When the tension in the piano string increases, its frequency will increases. Now since the beat frequency decreases, we can conclude that the frequency of piano string is $$251$$ $$Hz$$