18 A ray of light travels from air to glass. The incident ray makes an angle of 45 degrees while the refracted ray makes and angle of 30 degrees with the normal to the interface. The speed of light in air is 3.0×10 8 m/s. What is the of speed of light in glass? (a)2.12×10 8 m/s (b) 4.24×10 8 m/s (c)3.73×10 8 /s (d) 3.00×10 8 $/s
19 A 9V battery is short-circuited. The potential difference across the battery is found to be 8V, and the current is 5A. What is the internal resistance of the battery? (a) 0.1Ω (b) 0.2Ω (c)0.3Ω (d)0.4Ω
20 Ohm's law relates potential difference with? (a) power (b) Energy (c) current (d) time
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