PHYSICS

Senior six Physics paper 2 Assigment Please submit your answers as you sign in for first term, 2023 (a) Define the following as applied to convex mirrors: (i) Principal focus. (1 mark) (ii) Centre of curvature. (1 mark) (b) Describe an experiment to determine the radius of curvature of a concave mirror using a white screen with a hole and a wire gauze at its center, a source of light and a meter rule only. (5marks) (c) (i) Define linear magnification (1 mark) (ii) A finite object is placed at a distance d, in front of a concave mirror of focal length f. Show that the image formed is times the size of the object. (4 marks) (d) An extended real object is placed 15.0 cm in front of a convex lens of focal length 10.0 cm. A convex mirror having a radius of curvature of 20.0 cm is placed 45.0 cm behind the lens so as to be co-axial with it. Find the:- (i) nature and position of the final image formed. (4 marks) (ii) magnification produced. (2 marks) (iii) Sketch the ray diagram to show how the final image is formed. (2 marks) (a) (i) What is meant by a visual angle? (1 mark) (ii) Derive an expression for the magnifying power of a simple microscope in normal adjustment. (4 marks) (b) A student in a laboratory observes a cockroach using a magnifying glass. When his eye is far from the magnifying glass the insect appears to have coloured edges but on placing his eye very close to the device the insect is free from coloured edges. Explain his observations. (3 marks) (c) Two thin lenses, a convex lens L1 and a concave lens L2 of focal length 15 cm are carefully cemented together so as to form an achromatic doublet. A real object is placed 20 cm in front of L1 and remote from L2. A real image is formed 60 cm from L2. Find the focal length of L1 (3 marks) (d) (i) With the aid of a labelled diagram describe the structure and mode of operation of a slide projector. (5 marks) (ii) A slide projector having a projection lens of focal length 15 cm forms an image of area 4.0 m2 on the screen. If the object slide has dimensions 5.0 cm × 5.0 cm, determine the distance of the screen from the slide. (4 marks) 3. (a) (i) Define e.m.f and internal resistance of a battery. (2 marks) (ii) Describe an experiment to determine the internal resistance of a cell. (6marks) (b) The diagram in the figure 4 below shows two sources of e.m.f. of 6 V and 4 V having internal resistances of 2Ω and 3Ω respectively. The sources are connected in opposition to each other. Determine the reading of the voltmeter connected across PQ. (4 marks) (c) (i) Define temperature coefficient of resistance of a conductor. (1 mark) (ii) Explain why semi-conductors have a negative temperature coefficient of resistance. (3marks) (d) The resistance of an element of an electric fire is 50Ω at 200C. When operating at a 240V supply the current flowing through it is 5A. Calculate the steady temperature reached by an electric fire, if the temperature coefficient of resistance of the element is 2.0 x 10 -4K-1. (4 marks) 4. (a) (i) Define the term work function of a material. (1 mark) (ii) With the aid of diagrams, describe how two metal spheres can both be charged positively by induction. (5 marks) (b) (i) What is an equi-potential surface and state its characteristics. (3 marks) (ii) Explain why electric field lines are always normal to the surface of a charged conductor. (3 marks) (c) (i) Define the term charge density. (1 mark) (ii) Draw sketches showing the variation of charge density on a charged metal sphere and a charged pear shaped conductor. (3 marks) (d) An electron of charge 1.6 × 10 – 19 C, moves from rest into an empty space between two points 3 mm apart whose potential difference is 150 V. Find the; (i) Electric field intensity between the points. (2 marks) (ii) Energy acquired by the electron. (2 marks) 5. (a) Define capacitance of a capacitor and dielectric constant (2 marks) (b) Describe an experiment to determine the dielectric constant of a material placed to fill the space between the plates of a capacitor using a ballistic galvanometer. (6 marks) (c) A parallel plate capacitor of area A has the space between its plates filled with a dielectric material of dielectric constant εr and thickness d. Show that when the dielectric is half way withdrawn from the region between the plates, the new capacitance becomes where εo is the permittivity of air. (3 marks) (d) A capacitor of capacitance 47µF is used to power the flash gun of a digital camera. The average power output of the flash gun is 4.0 kW for a duration of 2 milliseconds. Calculate the (i) potential difference between the terminals of the capacitor just before the flash. (3) (ii) maximum charge stored by the capacitor. (2 marks) (iii) Average current provided by the capacitor during the flash and state any assumptions made. (3 marks)