IB Physics HL E.2 Quantum physics questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

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Question 1

Multiple choiceMedium1 mark

Two non-relativistic particles, X and Y, have masses $m$ and $2m$ and speeds $v$ and $3v$ respectively. Which row gives the momentum ratio $p_Y/p_X$ and de Broglie wavelength ratio $\lambda_Y/\lambda_X$

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Answer: A. For non-relativistic particles, $p=mv$ so $p_Y/p_X=(2m)(3v)/(mv)=6$ Since $\lambda=h/p$ $\lambda_Y/\lambda_X=p_X/p_Y=1/6$

B: treats wavelength as directly proportional to momentum. C: omits the mass difference when comparing momenta, giving $p_Y/p_X=3$ D: reverses the ratios, giving $p_X/p_Y$ and $\lambda_X/\lambda_Y$ instead.

Remember: de Broglie wavelength is inversely proportional to momentum.

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