Light

CHAPTER 5:LIGHT 1.(a). Diagram 9.1 shows a ray of light directed perpendicularly at a side of the semi circular glass block. The ray passes through the glass block to a point O before leaving the glass block. The angle of incidence in the glass block is 30°.

Diagram 9.1 (i) What is meant by angle of incidence? (ii) Explain how total internal reflection occurs in Diagram 9.1 above? [4 marks] (b) Diagram 9.2 and Diagram 9.3 show two rectangular glass blocks with different optical density and refractive index. Ray of light is directed toward the glass blocks with the same angle of incidence 30°. Density = 2600 kgm-3 Density = 2670 kgm-3

Diagram 9.2 Diagram 9.3 Based on Diagram 9.2 and Diagram 9.3, (i) compare the densities of the glass blocks. (ii) compare the refractive index of the glass blocks (iii) compare the angle of refraction of the glass blocks (iv) relate the angle of refraction, r and the density of the glass blocks. (v) relate the angle of refraction, r and the refractive index of the glass blocks [5 marks] (c) Diagram 9. 4 shows a fibre optic.

distance to the size of image that formed on the screen. [ 5 marks ]

You are required to give suggestions to design a fibre optics which can works efficiently. Using your knowledge on light, and the properties of material, explain the suggestion based on the following aspects; (i) the refractive index of outer and inner layer (ii) flexibility (iii) strength (iv) thickness (v) density of the glass 2.A slide projector is used to view an image from a slide. The power of the lens used by the projector slide is + 5D. (a) What is meant by power of lens?. [ 1 mark ] (b) A student used a slide projector to view the image from the slide. When the slide is place nearer to the lens the sharp image form on the screen as shown in Diagram 9.1. When the slide is place further from the lens the sharp image form on the screen as shown in

Based on Diagram 9.1 and Diagram 9.2, compare the object distance, the image distance and size of image that formed on the screen. Relate the object distance to the image distance and the object

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Diagram 9.4 (c) While driving a car on a hot day, you may see a mirage on the road. Explain how mirage occurred. [ 4 marks ] (d) Diagram 9.5 shows a simple astronomical telescope.

Diagram 9.5 By using two prism and a telescope in Diagram 9.5, suggest modification that can be done to make a binocular. In your explanation, (i) draw the arrangement of the prisms and lenses (ii) draw ray diagram to explain how the image form (iii) state two advantages using binocular compared to telescope when observing far object on the ground. [ 10 marks ] 3.(a) Diagram 9.1 and Diagram 9.2 show a transparent block made of a material with a different refractive index. A light ray travel in both blocks with the same incident angle, i.

(i) What is meant by a refractive index? [1 mark] (ii) Using Diagram 9.1 and Diagram 9.2, compare the refractive index, refraction angle and critical angle between the two blocks. Base on Diagram 9.1 and Diagram 9.2, relate the refractive index with critical angle. [5 marks]

(b) (i) State two conditions under which light ray would undergo total internal reflection. [2 marks] (ii) Diagram 9.3 shows a light ray is incident on a piece of Crown Glass of critical angle 42°.Draw the light ray to show how a ray emerging from the Crown Glass DIAGRAM 9.1

(c) Diagram 9.4 shows the structure of an optical fibre used in telecommunications.

Optical fibres are made of fine strands of glass. Each single glass fibre (inner core) is coated with a thin layer of another type of glass (outer cladding).You are required to give some suggestions in designing an optical fibre which can carry more information. Explain your suggestions base on the following aspects: (i) refractive index of the inner and outer glass (ii) the properties of material used for optical fibre (iii) the thickness of the glass [10 marks] 4. Diagram 10.1 and Diagram 10.2 show light rays from two identical objects passing through a convex lens.Both situations produce real images. F is the focal point for the convex lens

(a) (i) What is meant by real image? [1 mark] (i) Based on Diagram 10.1 and Diagram 10.2, compare the object distance, the image distance and the size of image. Relate the size of the image with the image distance to make a deduction regarding the relationship between the object distance and the size of the image. [5 marks] (b) Describe how you estimate the focal length of a convex lens. [4 marks] (c) You are given two convex lenses, R and S, with focal lengths of 40 cm and 10 cm respectively. Both the lenses are used to build a compound microscope. (i) Using the two lenses, explain how you would build a compound microscope. [6 marks] (ii) Suggest a suitable optical device to modify the microscope you built in (c)(i) to produce brighter image. (c)(i) supaya menghasilkan imej yang lebih jelas. [2 marks] (iii) Suggest and explain a method to produce a bigger image in the compound microscope. [2 marks] 5.Diagram 9.1 and Diagram 9.2 show the parallel rays of light directed towards the convex lenses J and K. Both the lenses produce real images. F is the focal point for each lens.

DIAGRAM 9.2 (a) (i) What is meant by focal length? [1 mark] (ii) With reference to Diagram 9.1 and Diagram 9.2, compare the thickness of the lenses and the effects it has on the refracted rays to make a deduction regarding the relationship between the thickness of the lenses and their focal length. [5 marks] (b) Diagram 9.3 shows the ray diagram of a simple microscope.

Fe : Focal point of eyepiece. Fo : Focal point of objective lens.

DIAGRAM 9.3 (i) State the function of the eyepiece.

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[1 mark]

(ii) State the characteristics of the image formed by a microscope. [3 marks] (c) You are given two convex lenses S and Q of different focal length. Lens S has a longer focal length than lens Q. (i) Using the two lenses above explain how are you would make a simple astronomical telescope. [4 marks] (ii) Suggest modification that need to be done on the telescope to produce clearer and bigger images. [6 marks]

6.Diagram 9.1 and 9.2 show light rays passing through a convex and a concave lenses.

(a)(i) Define reflective index of a medium [1 mark] (ii) With reference to Diagram 9.1 and 9.2, compare the light ray before and after passing through both lenses. And then deduce a physics concept. [5 marks] (b) Explain why a fish in a pond able to see objects around although there are obstacles. [4 marks] (c) You are given two right angles prisms to build a periscope (i) Explain how you are going to build a periscope. [6 marks] (ii) Suggest modification to be made to convert the periscope to binoculars [4 marks]

(d) Figure 9(d) shows a man who is standing in a swimming pool.

On a hot and sunny day, a driver sees a pool of water on the road in front of him. The position of driver and the pool of water are as shown in Figure 9(b). (a)(i) Explain the meaning of refractive index [1 mark] (ii) Based on your observations in the above figures, state the common characteristics. Relate the above common characteristics to deduce a relevant physics concept. [5 marks] (b) Which mirror is used as the rear mirror of vehicles? Explain your answer. [3 marks] (c) Figure 9(c) below shows a spear which was thrown by a fisherman towards a fish in a pool.

(ii)

State your observation on the length of his feet and explain your observation. [3 marks] The depth of water is 0.4 m. calculate the distance of the image of the foot at point P from the surface of the water. [Refractive index of water = 1.33]

8. Figure 4 shows two ways of making a fire

Figure 4 (a) (i) (ii)

7. Figure 9(a) shows a submarine which uses a periscope to see objects above the water surface.

(i)

(iii)

Given that the spear did not hit the fish, explain the observation. [3 marks] Draw a ray diagram to show how the image of the fish is formed. [2 marks] Suggest a way which can be used by the fisherman so that the spear hit the target. [ 1 mark]

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(b)

i. What are the energy changes involved? [1m] ii. Based on your observations of the first and second situations, describe the characteristics that differ in the situations. Then correlate the characteristics to develop a physics concept [5m] At the beginning of the century, a scientist by the name of Archimedes successfully drove off enemy ships with

the help of women and children using only mirrors. How did the women and children help Archimedes? [4m] (c)

Periscope using prisms are better than those using mirrors i. How does the prismatic periscope function? [4m] ii. How can a prismatic periscope be modified to see distant object [6m]

Explain what happens to the image if (i) the girl moves backwards 2 m (the focal length is 0.8 m) (ii) the concave mirror replaced with convex mirror You may use the diagram to illustrate your answers. [4 marks] (d) You are given two pieces of plane mirrors measuring 4 cm x 5 cm and a long cardboard tube to make a periscope. (i) Using the plane mirrors and other materials, describe how you would make the periscope. (ii) Explain why the images observed through the periscope using plane mirrors are not very clear. (iii) Suggest modification that can be made to the periscope to produce clearer and bigger images. [10 marks]

9.(a) Diagram 7.1 shows the parallel rays of light directed towards the concave mirrors P and Q. In each diagram, C is the centre of curvature, CM is the radius of curvature of the mirror and F is the focal point of the lens.

(a) What is meant by centre of curvature? [1 mark] (b) Using Diagram 7.1 and Diagram 7.2, compare the curvature of mirrors P and Q and the effects on reflected rays. State the relationship between the curvature of the mirrors and their focal lengths. [5 marks] (c) Diagram 7.3 shows a girl standing in front of a concave mirror. The image formed in the mirror is virtual image and bigger than original size.

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