8. Colours are often observed when gasoline is pouted onto water. This effect is primarily produced by a) Diffraction d) Absorbtion b) Diffuse Reflection e) Incandescente c) Interference 9. The type of electromagnetic radiation that travels at the greatest speed is a) Radio waves d) Gamma rays Visible light e) They all travel at the same speed c) X-Rays 10. Figure 2 below shows three experiments for studying the interaction of monochromatic light with thin films of glass of various thickness t. The eye represents the position of the observer. The observer sees constructive interference in a) I only d) I and Ill only b) Il only e) ll and Ill only c) Ill only CIID Figure 2 Short Answer - Neatly provide written responses 11. Explain why the wavelength of light decreases when it passes from a vacuum into a material. State which properties change and which stay the same. [2 marks]