CBSE ADDA

Class 8 light and vision (reflection and eye) leanwell science/Basic science Q. Why are multiple images are formed when two mirror are placed at an angle to each other ? Ans: This happen because image formed by first mirror act as an object for 2nd mirror. No of image = (360/ q ) -1[0 degree or Parallel to each other --> Infinite number] Q. What do you mean by persistence of vision? Ans : Image of an object retain on retina for 1/16 th of a sec even after removed is called persistence of vision. This form the basis of the principle of cinematography. Q. How persistence of vision form basis of the principle of cinematography? Ans: in moving cinema, we take still pictures. The sequence of still pictures are projected on screen at rate of 24 images per second (persistence of vision is 1/16th of sec.)The successive images merge smoothly and give us feeling of movie. Q. A person whose retina is damaged cannot see why? Ans: This happens because retina acts as seen o

Class 10 our environment board solved Questions 2016 1. What is the function of ozone in upper atmosphere? Ans: It shields the surface of the earth from ultraviolet rays from the Sun. 2. Why should biodegradable and non biodegradable waste be discarded in two separate dustbins? Ans: So that the time and energy required in segregation may be saved and waste may be disposed off quickly 3. The following organisms form a food chain. Which of these will have the highest concentration of non-biodegradable chemicals ? Name the phenomenon associated with it. Insects, Hawk, Grass, Snake, Frog. Ans: Hawk ; Biomagnifications 4.. Write the full name of the group of compounds mainly responsible for the depletion of ozone layer. Ans: Chloroflurocarbons 5. List two examples of natural ecosystem. Ans: Forests ,Ponds,Lakes 6. Differentiate between biodegradable and non-biodegradable substances with the help of one example each. List two changes in habit that people must adopt to dispose non-biodegrad

Practice these questions to excell in exam 2016 Class 9 maths SA2 Question paper - 1 Download File Class 9 maths SA2 Question paper - 2 Download File Class 9 maths SA2 Question paper - 3 Download File Class 9 maths SA2 Question paper - 4 Download File Class 9 maths SA2 Question paper - 5 Download File Class 9 Science SA2 Question paper - 1 Download File Class 9 Science SA2 Question paper - 2 Download File Class 9 Science SA2 Question paper - 3 Download File Class 9 Science SA2 Question paper - 4 Download File Class 9 Science SA2 Question paper - 5 Download File Formore papers visit  class 9 Question paper for exam2015 SA2

Diversity in Living Organisms solved CBSE Paper-5 Oswal Question Bank Diversity in Living Organisms         Do wnload File Very Answer type Questions [1 mark each]   1.State the phylum to which centipede and prawn belong. (Board 2013) Answer: Arthropoda.          2. In which kingdom would you place an organism which is single called, eukaryotic and photo- synthetic? (Board 2013) Answer:  Protista. 3.Rewrite the scientific name correctly : (i) panthera tigris (ii) periplaneta Americana. (Board 2012.,  501004) Answer:  (i) Panthers tign's  (ii) Periplaneta americana. 4.Name the term which is used for the following (i) The left and right halves of the body have the same design. (ii) Animal tissue defferentiate from the three embryonic germ layers. (Board 2012, 501005; 47023) Answer:  (i) Bilaterally symmetrical. (ii) Triploblastic.        5.Name the phylum to which Prawn and Centipede belong. (Board 2012, SC-1008; 47001, )  

1.A submarine enters a sonar pulse, which returns from an under water cliff in 1.02 s. If the speed of sound in salt water is 1531 m/s, how far away is the cliff? Ans: t = 1.02s, v = 1531m/s Now d=s x t Distance travelled by sonar pulse = 2d = 2x1531x1.02 = 1561.62m Distance of the cliff = d/2= 1561.62/2 = 780.81m 2. If the tension in the wire is increased four times how will the velocity of wave in a string varies? Answer: velocity of the wave in string is directly proportional to the square root of the tension thus if tension is increased 4 times the velocity will be doubled. 3. What is Echo. Explain the conditions that have to be satisfied to hear an echo? Ans: reflection of sound wave from a large obstacle is called an echo. The most important condition for hearing an echo is that the reflected sound should reach the ear only after a lapse of at least 0.1 second after the original sound dies off and the obstacle is at least at a distance of 17 m 4. Why do echoes produced in an

Solved problems:Class 9 _Atoms and Molecules  1. Q. 5 g of calcium combine with 2 g of oxygen to form a compound. Find the molecular formula of the compound. (Atomic mass of Ca = 40 u; O = 16 u)  Ans. Number of moles in 5g of calcium = mass / molar mass    =5 /40    =  0.125  Number of moles in 2g of oxygen = mass / molar mass         =  (2 / 16)  =  0.125 Now we will calculate the simplest ratio of the element by dividing the number of moles of each element by the smallest value.  Since number of moles of each element is 0.125, therefore calcium and oxygen are present in a ratio of 1 : 1. Thus the empirical formula of the compound is CaO. For calculating the molecular formula, we need the molecular mass of the compound. However, because a compound with the formula CaO is known, Therefore the molecular formula of the compound is CaO. . Q. (i) Name the body which approves the nomenclature of elements and compounds.

Fully Solved Questions from previous year board Paper Question: 1. What causes buoyant force (or up thrust) on a boat? Answer: Buoyant force is due to volume of boat and density of water. Question: 2. what is the cause of buoyant force? Answer: : The pressure difference on lower part and upper part of a body cause of buoyant force . Question: 3. An Object of volume V is immersed in a liquid of density P. Calculate the magnitude of buoyant force acting on the object due to the liquid Answer: Vd g Question: 4. why does a block of wood held under water rise to the surface when released? Answer: This happens because as upward force is greater than the weight. Question: 5. What happens to the buoyant force as more and more volume of a solid object is immersed in a liquid. When does the buoyant force become maximum? Answer: The buoyant force exerted by a fluid is equal to the weight of fluid displaced. Therefore the buoyant force increases as more and more vol