TE Enriched Sample (E)

Chapter Exercise 33 6. Which of the following statements is/are advantages of using LED lamps over conventional incandescent lamps? (1) The brightness of LED lamps can be easily controlled by varying the pd across the lamps. (2) LED lamps can produce a spectrum more similar to that of sunlight. (3) The typical lifetime of LED lamps is much longer than that of incandescent lamps. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only 7. A lamp is placed 1 m vertically above the centre of a circular table of radius 1 m. What is the ratio of the illuminance on the brightest surface to that on the dimmest surface? A. 2 : 1 B. 2 : 1 C. 8 : 1 D. 4 : 1 8. A light source is illuminating a small surface as shown. If the luminous flux produced by the lamp is Φ , what is the illuminance on the surface? A. ° cos 4 2 30 2 3 r U B. ° cos 4 2 30 2 r U C. ° cos 4 2 60 2 3 r U D. ° cos 4 2 60 2 r U 9. Two small surfaces X and Y are on two walls perpendicular to each other. Initially, a small light source O is equidistant from them such that OX = OY = 1 m. The source is then moved due north by 1 m. Which of the following statements is/are correct? (1) Initially, X and Y have the same illuminance. (2) The actual illuminance on X and Y depends on the colours of the walls. (3) After the move, X has a smaller illuminance than Y . Y X 1 m 1 m O N A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only 10. Two parallel small surfaces A and B are illuminated by a small lamp as shown. Light is incident normally on B . What is the ratio of illuminance on A to that on B ? Given that cos 45 2 1 c = . lamp 45° B A 1 m A. 2 : 2 B. 2 : 2 C. 2 : 4 D. 4 : 2 11. A parallel beam of light strikes a small surface at different angles of incidence θ . Which of the following graphs best shows how the illuminance on the surface E varies with θ ? A. E 0 θ B. E 0 θȱ C. E 0 θ D. E 0 θȱ 12. HKDSE 2012 Which of the following lamps has the greatest end-use energy efficiency? luminous flux power rating A. 750 lm 15 W B. 900 lm 30 W C. 750 lm 60 W D. 600 lm 90 W 2 m 30° (1.3) B (1.3) C (1.3) B (1.2) A (10%) (80%) (1.1 & 1.2) Q3.1 A (1.3) B (1.3) C Sample © United Prime Educational Publishing (HK) Limited, Pearson Education Asia Limited 2023 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publishers.