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A coin placed at the bottom of a beaker appears to be raised by 4.0 cm. If the refractive index of water is 4/3, find the depth of the water in the beaker.
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What is meant by ‘MCB’? Which part of the domestic electric circuit does it replace?
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The refractive index of glass with respect to air is 1.5. What is the value of the refractive index of air with respect to glass?
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What is a switch? State its function in an electric circuit.
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What are ‘dual switches’? Mention their one main use.
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Why should switches always be connected to the live wire? Give one precaution that should be taken while handling switches.
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Two astronauts cannot hear each other on the moon. Why?
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Explain why does a wine glass starts rattling, when a note of some particular frequency is struck by a piano?
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Explain why strings of different thicknesses are provided on a stringed instrument.
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What do you mean by electron emission?
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What are the types of emission?
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State two characteristics of the substance used as thermionic emitter.
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State two properties that a substance should possess when used as a thermionic emitter.
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How is a cathode ray beam affected while passing through a magnetic field?
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How is a cathode ray beam affected while passing through an electric field?
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What are cathode rays? Why are they called ‘cathode rays’? Name a material which exhibits fluorescence when cathode rays fall on it.
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How is a zinc sulphide screen affected when a cathode ray beam strikes it?
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