8 12 The diagram shows a transparent tank, with thin plastic sides, that can be used to determine the refractive index of a transparent liquid. transparent plastic tank Not to scale light source card w s t A rectangle of opaque card is stuck on the side of the tank containing the liquid. A light source is placed in front of the tank and the width s of the shadow of the card, which is formed on the back of the tank, is measured. The width t of the card and the width w of the tank are also measured. (a) The angle of incidence of the light as it enters the tank is 7.2° Show that the refractive index of the liquid is about 1.4 w = 35.0 cm t = 4.0 cm s = 10.2 cm (3) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................ ................................................................... .................................................................................................................................................................................................................................................. . Turn over 9 (b) Determine the speed of light in the liquid. (2) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... Speed of light = .................................................................... (Total for Question 12 = 5 marks)