IB Physics HL C.2 practice question

Question 1

Multiple choiceMedium1 mark

A source produces periodic waves in medium X with wavelength $\lambda$ period $T$ and speed $v$ The source is adjusted to produce waves with period $T/2$ in medium Y, where their speed is $3v$ What is the wavelength of the waves in medium Y?

Show answer and explanation

Answer: B. Since $v=f\lambda$ and $f=1/T$ wavelength is $\lambda=vT$ The wavelength in medium Y is $(3v)(T/2)=3vT/2=3\lambda/2$

A: applies the period change but leaves the wave speed unchanged.
C: applies the speed change but leaves the period unchanged.
D: uses $2T$ instead of $T/2$ then applies the speed factor of 3.

Remember: wavelength is the product of wave speed and period.

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