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Physics

CAIE2024

Electrons in a vacuum are accelerated from rest through a potential difference (p.d.) V to form a beam. The electrons each have mass m and charge q. The beam is incident on a graphite crystal that acts as a diffraction grating. After passing through the crystal, the beam reaches a fluorescent screen. An interference pattern is observed on this screen. (a) Explain what this observation shows about the nature of electrons. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (b) Determine an expression, in terms of m, q and V, for the momentum p of an electron in the beam. p = ......................................................... [3] (c) The p.d. through which the electrons are accelerated is now increased to a greater value. Describe and explain the effect of this change on the interference pattern observed. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (cid:300)(cid:205)(cid:266)(cid:190)(cid:288)(cid:180)(cid:237)(cid:200)(cid:245)(cid:207)(cid:298)(cid:197)(cid:266)(cid:224)(cid:251)(cid:183)(cid:260)(cid:215) © UCLES 2024 (cid:300)(cid:236)(cid:185)(cid:252)(cid:207)(cid:287)(cid:274)(cid:253)(cid:218)(cid:251)(cid:239)(cid:291)(cid:297)(cid:271)(cid:276)(cid:289)(cid:296)(cid:258) 9702/42/O/N/24 (cid:293)(cid:229)(cid:245)(cid:213)(cid:245)(cid:245)(cid:229)(cid:245)(cid:261)(cid:181)(cid:277)(cid:197)(cid:197)(cid:245)(cid:229)(cid:245)(cid:213)(cid:213) NIGRAM SIHT NI ETIRW TON OD NIGRAM SIHT NI ETIRW TON OD NIGRAM SIHT NI ETIRW TON OD NIGRAM SIHT NI ETIRW TON OD NIGRAM SIHT NI ETIRW TON OD PMT * 0000800000021 *

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