Sound waves

Tested in 5 real MPSC questions across 3 years (2017–2021). See it in context on the interactive Concept Graph →

Years it was asked

2021 2020 2017

What you need to know first

Audible frequency rangeMechanical wavesBoundary conditions for wavesFormula v = fλFormula Distance = speed × timev = f * lambda formulaHuman hearing frequency range

Real questions that test this

श्रव्यातीत तरंग असे तरंग आहेत की ते Ultrasonic waves are those waves which

a)(1) मानव ऐकू शकत नाही / human beings cannot hear&check; Correct

b)(2) मानव ऐकू शकतो / human beings can hear

c)(3) त्यांची वारंवारता कमी आहे / have less frequency

d)(4) वरीलपैकी एकही नाही / None of the above

Ultrasonic waves have frequencies above the human hearing range (greater than 20 kHz), hence they cannot be heard by human beings.

प्रकाश तरंग मुख्यत: ____________ स्वरूपात असतात. Light is generally in the form of :

1)चुंबकीय तरंग / Magnetic Waves

2)विद्युत तरंग / Electrical Waves

3)विद्युत चुंबकीय तरंग / Electromagnetic Waves&check; Correct

4)वरीलपैकी एकही नाही / None of the above

Light travels in the form of electromagnetic waves, specifically transverse waves.

जेव्हा एखाद्या ध्वनी तरंगाचे संपीड़न दृढ भंतीवर आदळेल तेव्हा त्याचे प्रतिबिंबित रूप हे : When a compression of sound waves is incident on rigid wall, it is reflected as :

1)180 अंशानी (π) अवस्था संकुचीत होईल. / Compression with a phase change of π (by 180°)

2)अवस्था बदल होणार नाही. / Compression with no phase change&check; Correct

3)90 अंशानी (π/2) अवस्था विरलन होईल. / Rarefaction with a phase change of π/2 (by 90°)

4)विरलन होईल पण अवस्था बदलणार नाही. / Rarefaction with no phase change

When a compression of a longitudinal sound wave strikes a rigid wall, it reflects back as a compression with a phase change of 180 degrees or reversal, but compression remains compression (unlike a fixed end string where it inverts, sound pressure reflection at a rigid boundary reflects compression as compression). Wait, actually at a rigid wall, particle velocity has a node and pressure has an antinode, meaning a compression reflects as a compression.

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