JEE MAIN - Physics (2019 - 12th April Evening Slot - No. 3)
A tuning fork of frequency 480 Hz is used in an experiment for measuring speed of sound (v) in air
by resonance tube method. Resonance is observed to occur at two successive lengths of the air column,
l1 = 30 cm and l2 = 70 cm. Then, v is equal to -
338 ms–1
384 ms–1
379 ms–1
332 ms–1
Explanation
We know,
$$\lambda $$ = 2($${l_2} - {l_1}$$)
given $${l_2}$$ = 70 cm and $${l_1}$$ = 30 cm
$$ \therefore $$ $$\lambda $$ = 2(70 - 30) = 80 cm
Also we know, v = $$\lambda $$$$f$$ = 0.8 $$ \times $$ 480 = 384 m/s
$$\lambda $$ = 2($${l_2} - {l_1}$$)
given $${l_2}$$ = 70 cm and $${l_1}$$ = 30 cm
$$ \therefore $$ $$\lambda $$ = 2(70 - 30) = 80 cm
Also we know, v = $$\lambda $$$$f$$ = 0.8 $$ \times $$ 480 = 384 m/s
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