5 Turn over 7 An electron travels at a velocity v. Which of the following is the correct expression for the de Broglie wavelength λ of the electron? A λ = 3 00 10 9 11 10 8 31 . . × × × − v B λ =  9 11 10 3 00 10 31 8 . . × × × − v C λ = 6 63 10 9 11 10 34 31 . . × × × − − v D λ =  9 11 10 6 63 10 31 34 . . × × × − − v (Total for Question 7 = 1 mark) 8 In an experiment to determine the wavelength of light, three values for the wavelength are obtained and the mean value calculated. Wavelength / nm 466 448 473 Mean wavelength / nm 462 What is the uncertainty, in nm, in these results? A 25 B 18 C 14 D 11 (Total for Question 8 = 1 mark)