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