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MADHUSTHALI VIDYAPEETH F.M 80 Time 2h Date : FIRST ASSESSMENT : 2019-2020 SUBJECT: PHYSICS CLASS- X SECTION A Attempt all questions from this section Question 1 a) State the energy changes in the following cases while in use: (i) An electric iron. (ii) A ceiling fan. b) The diagram below shows a lever in use: [2] [2] (i) To which class of levers does it belong? (ii) Without changing the dimensions of the lever, if the load is shifted towards the fulcrum what happens to the mechanical advantage of the lever? c) The power of a lens is - 5D. [2] (i) Find its focal length. (ii) Name the type of lens. d) (i) State the relation between the critical angle and the absolute refractive index of a medium. (ii) Which colour of light has a higher critical angle? Red light or Green light. [2] e) The following diagram shows a 60 , 30 , 90 glass prism of critical angle 42 , Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface. [2] Question 2 a) (i) Why is the ratio of the velocities of light of wavelengths 4000 AO and 8000 AO in vacuum 1:1? (ii) Which of the above wavelengths has a higher frequency? [2] O b) A type of electromagnetic wave has wavelength 50A . (i) Name the wave. (ii) State one use of this type of wave. [2] c) (i) Name the radiations which are absorbed by greenhouse gases in the earth s atmosphere. (ii) A radiation X is focused by a particular device on the bulb of a thermometer and mercury in the thermometer shows a rapid increase. Name the radiation X. [2] d) (i) Name a prism required for obtaining a spectrum of Ultraviolet light. (ii) Name the radiations which can be detected by a thermopile. [2] e) Why is the colour red used as a sign of danger? [2] This paper consists of four printed pages.
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