Speed of Sound (v = f lambda) MCQs

Q1. Two notes, 250 Hz and 500 Hz, travel in the same air. Which has the longer wavelength?

• A.the 250 Hz note (lower frequency)
• B.the 500 Hz note
• C.both equal
• D.neither has a wavelength

Answer: A. the 250 Hz note (lower frequency)

Q2. In which medium does sound generally travel fastest?

• A.steel (a solid)
• B.air (a gas)
• C.vacuum
• D.water, faster than steel

Answer: A. steel (a solid)

What's the underlying rule? Apply the wave equation v = f * lambda to the given sound wave; substitute the supplied parameters into this relation => the unknown quantity is isolated and evaluated; therefore the listed value = steel (a solid). Does that line up with one of the options? Yes - Correct. And the rest? option B) 'air (a gas)' is incorrect: Sound is slowest in gases; option C) 'vacuum' fails since Sound cannot travel in a vacuum at all. Pick: A) steel (a solid).

Q3. Which factor does NOT change the speed of sound in a given gas?

• A.the loudness of the sound
• B.the temperature of the gas
• C.the nature of the gas
• D.the humidity of the air

Answer: A. the loudness of the sound

Diagnose the question type - a typical physics numerical. We are after the quantity the stem asks for. Tool of choice - v = u + a*t or s = u*t + (1/2)*a*t^2. Rearrange it for the unknown before substituting. Numbers in: v = u + a*t or s = u*t + (1/2)*a*t^2. Common-sense check: write the kinematic relation that links the named quantities, e.g. Lock in option A) the loudness of the sound. Trap-watch: option B) 'the temperature of the gas' is wrong because Temperature does change the speed of sound; option C) 'the nature of the gas' misses the point - Different gases give different sound speeds.