Q145 / 150 · MHT CET 2026 (13 April Shift 2) · Physics
Sound waves travel at $350$ m/s through a warm air and at $3500$ m/s through brass. Which of the following is correct about the wavelength of a $700$ Hz accoustic wave as it enters brass from warm air?
- AIt increase by a factor $20$
- BIt decrease by a factor $10$
- Correct answerCIt increase by a factor $10$
- DIt decrease by a factor $20$
Solution
When a sound wave travels from one medium to another, its frequency $f$ remains constant.
The wavelength $\lambda$ is given by the relation $v = f \lambda$, which implies $\lambda \propto v$.
Given the speed of sound in warm air $v_1 = 350$ m/s and in brass $v_2 = 3500$ m/s.
The ratio of the wavelengths in the two media is:
$\dfrac{\lambda_2}{\lambda_1} = \dfrac{v_2}{v_1} = \dfrac{3500}{350} = 10$
Thus, the wavelength increases by a factor of $10$.
Answer: It increase by a factor $10$
The wavelength $\lambda$ is given by the relation $v = f \lambda$, which implies $\lambda \propto v$.
Given the speed of sound in warm air $v_1 = 350$ m/s and in brass $v_2 = 3500$ m/s.
The ratio of the wavelengths in the two media is:
$\dfrac{\lambda_2}{\lambda_1} = \dfrac{v_2}{v_1} = \dfrac{3500}{350} = 10$
Thus, the wavelength increases by a factor of $10$.
Answer: It increase by a factor $10$
Hence, the correct answer is option: 'C'.