7 A ray of light travelling from air to glass has an angle of incidence of 370. Its speed in air is 3.0x 10 m/s and its wavelength in air is 5.0 x10 m. If the speed of light in the glass is 2.0 x10 m/s, calculate: (a) the frequency of the light in both air and glass (b) the angle of refraction (c) the wavelength of light in the glass (d) the refractive index for glass. 8. In an experiment to measure the refractive index of glass, the incident angles and corresponding refracted angles of several light rays were measured. The results are shown below: Incident angle, i Refracted angle, r 20 13 30 19 40 25 50 30 60 35 70 38 80 40 (a) Copy the table and include two additional columns for values of sin i and sin r. (b) Plot a graph of sin i (y-axis) against sin r (x-axis) by drawing the "best-fit" line. (c) Calculate the gradient of the graph. What is the significance of the gradient? 9. A ray of light travelling in air is incident onto a mirror at an angle of 50 as shown in figure 3. It is reflected from the mirror and then enters water of refractive index 1.3. Calculate the refracted angle in the water. Fig. 3 MIRROR M