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WAEC Physics 2021 Theory — Question 7

Question 7 of 35 from the West African Examinations Council (WAEC) Physics 2021 Theory paper, with the correct answer and a full explanation.

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5(b). A particle of wavelength 4.2×10⁻¹¹ m travels with a momentum of 1.6×10⁻²³ kg ms⁻¹. Determine the value of Planck's constant, h.

Model answer

Using de Broglie's equation λ=h/p, h=λp = 4.2×10⁻¹¹×1.6×10⁻²³ = 6.72×10⁻³⁴ Js.

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