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light - Reflection and refraction Exercises Questions Page no 212 1. Which one of the following materials cannot be used to make a lens? a) Water b) Glass c) Plastic. d) Clay Ans:-( d ) Explanation :- Because clay is an opaque substance and it doesn't allow the light to pass through it. 2. The image formed by a concave mirror is observed to be virtual ,erect and larger than the object .Where should be the position of the object? a) Between the principal focus and the centre of curvature b) At the centre of curvature c) Beyond the centre of curvature d) Between the pole of the mirror and it's principal focus. Ans: -( d ) Explanation :- one and only condition that forms a virtual image using concave mirror is, the position of the object placed between pole and foc...

Acids, Bases and Salts textual questions Textual Questions 1. Which of the statements about the reaction below are incorrect?(1 mark) 2PbO(s) + C(s) →2Pb(s) + CO2(g) (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced (i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all Ans:- (i) is correct. Explanation : The statements (a) and (b) are incorrect 2. Fe 2 O 3 + 2Al → Al 2 O 3 + 2Fe (1 mark) The above reaction is an example of a (a) combination reaction. (b) double displacement reaction. (c) decomposition reaction. (d) displacement reaction. Ans: - (d). Explanation : This is an example of displacement reaction...

Acids, Bases and Salts textual questions Chapter:- 2. Acids, Bases and Salts textual questions 1.Five solutions A, B, C, D and E when tested with universal indicator showed p H as 4, 1, 11, 7, and 9, respectively, which solution is (AS 1 ) (a) neutral (b) strongly alkaline (c) strongly acidic (d) weakly acidic (e) weakly alkaline Arrange the p H in increasing order of hydrogen ion concentration. Ans:- p H VALUE NATURE OF THE SUBSTANCE p H < 7 ACID p H < 7 and is closer to 0 STRONG ACID p H < 7 and is closer to 7 WEAK ACID p H > 7 BASE p H > 7 and is closer to 14 ...

chapter 1:- Heat Synopsis Videos TQs Bits short notes 1.Heat Heat is a form of energy which flows from the body at higher temperature to the body that has lower temperature. (from hot body to cold body.) Formula :- Q=ms∆t Where Q= heat (absorbed or lost) m = mass ∆t = temperature difference Units :- 1. joule (J) in S.I system) 2. calorie(cal) (in C.G.S system) 3. I cal = 4.186 joules. 5. Calorie: The amount of heat required to raise the temperature of 1 gram of water by 1 ° C is called calorie. 2.Temperature (T) 1. The degree of hotness or coldness is called temperature. 2. It depends on the average kinetic energy of the molecules of a system. 3. Units:- a. kelvin(K) (in S.I system) b. degree celsius(in C.G.S system) 4. Normal temperature of a healthy human is 98.6° F or 37° C o...