19 20 Assertion A compass needle is placed near a current carrying wire. The deflection of the compass needle decreases when the magnitude of the current in the wire is increased. Reason The strength of a magnetic field at a point near the conductor increases on increasing the current. Assertion: Biodegradable substances result in the formation of compost and natural replenishment. Reason: It is due to breakdown of complex inorganic substances into simple organic substances. 21 Dil. HCl is added to Zn granules." How will you prove that chemical change has taken place here? Support your response with two arguments. 22 State the post-fertilisation changes that lead to fruit formation in plants. 23 What is the purpose of making urine in the human body? Name the organs that stores and releases the urine. OR Why do arteries have thick and elastic walls whereas veins have valves? 24 The refractive indices of three media are given below: Medium A Refractive Index 1.6 B 1.8 1.5 A ray of light is travelling from A to B and another ray is travelling from B to C. (a) In which of the two cases the refracted ray bends towards the normal? (b) In which case does the speed of light increase in the second medium? Give reasons for your answer.