UNIQUE SCIENCE ACADEMY

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1 UNIQUE SIENE EMY Test (Unit 4) Refraction only Name :... Paper: Physics ate :... lass: II Time llowed: 35Minutes Maximum Marks: 25 Theory Section: [Total 6 Marks] Fig.. and Fig..2 show rays of light passing through the same semi-circular block of plastic. Q Q Fig.. Fig..2 Q is the centre of the straight side of the block. (a) State the value of the critical angle in the plastic. critical angle =... [] (b) Explain what is meant by the critical angle.... [2] (c) alculate the refractive index of the plastic. State the formula that you use. refractive index =... [2] (d) Some light reflects back into the plastic at Q. On Fig.., draw the reflected ray at Q. [] [Total 5] edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

2 2 Fig. 2. shows part of an optical fibre. 2 Q P R Fig. 2. The ray PQ undergoes total internal reflection in the optical fibre. (a) On Fig. 2., continue the path of ray PQ until it reaches end R. [] (b) Explain what is meant by total internal reflection.... [] (c) Optical fibres are cheaper and lighter than copper wires. State one other advantage of using optical fibres rather than copper wires for telephone communications.... [] (d) The light in the optical fibre is travelling at a speed of m / s and has a wavelength of m. alculate the frequency of the light. frequency =... [2] [Total 5] edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

3 3 Fig.3. shows an bubble in water. The rays of light are incident on the bubble. 3 ray ray 2 ray 3 water bubble Fig.3. The angle of incidence of ray on the bubble is greater than the critical angle. The angle of incidence of ray 2 on the bubble is less than the critical angle. Ray 3 is perpendicular to the surface of the bubble. The angle of incidence of ray 2 on the bubble is 27 and the angle of refraction of ray 2 inside the bubble is 37. (a) On Fig.3., at the point where ray meets the bubble, mark (i) (ii) the normal to the surface, the angle of incidence. [2] (b) omplete Fig.3. to show how all three rays continue after they meet the bubble. [3] (c) (i) efine what is meant by the refractive index of water (ii) alculate the refractive index of water. refractive index = [] [Total 6] edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

4 MQ SETION: [Total 9 Marks] The diagram shows the passage of a ray of light through a triangular block. What is the critical angle of light in? 4 2 ray of light enters a block at an angle of incidence i producing an angle of refraction r in the. i r block Several different values of i and r are measured, and a graph is drawn of against. Which graph is correct? edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

5 5 3 ray of red light enters a semi-circular block normal to the curved surface. Which of the following correctly shows the partial reflection and refraction of the ray? 4 In which of the diagrams is the path of the light ray not correct? water perspex edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

6 6 5 semi-circular block is made from a plastic. ray of light passes through it at the angles shown plastic To two decimal places, what is the refractive index of the plastic? The diagram shows four rays of light from a lamp below the surface of some water. What is the critical angle for light in water? water lamp edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

7 7 What happens to light as it passes from into? 7 Its frequency decreases because its speed decreases. Its frequency increases because its speed increases. Its wavelength decreases because its speed decreases. Its wavelength increases because its speed increases. 8 For a certain parallel-sided block, the value of is.50. ray of light passes through the block and emerges at an angle of 60 to the surface of the block. X 60 What is the value of the angle marked X? edicated to Mohammad Irtaza Haider Zain. ode 5054 [Turn over

8 8 9 ray of light is incident on one side of a rectangular block. Its path is plotted through the block and out through another side. Which path is not possible? MQ nswer Sheet edicated to Mohammad Irtaza Haider Zain. ode 5054