A student sitting at the back of a class is not able to see what is written on the blackboard. What defect of vision is he suffering from ? Which lens (convex or concave) should be used to correct the defect ?

A student has difficulty in reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected ?

Shyam a student has difficulty in reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected ? Explain with help of appropriate diagram .

Which lens from the following, should a person suffering from near-sightedness use?

Give scientific reasons for the following statements: To rectify the defect of near-sightedness or myopia, concave lens of suitable focal length is used as corrective lens.

There are 40 students in Class X of a school of whom 25 are girls and 15 are boys. The class teacher has to select one student as a class representative. She writes the name of each student on separate cards, the cards being identical. Then she puts cards in a box and stirs them thoroughly. She then draws one card from the box. What is the probability that the name written on the card is the name of (i) a girl? (ii) a boy?

You may have seen the trick where a tablecloth is jerked from a table, leaving the dishes that were on the cloth nearly in their original positions. What do you need to perform this successfully? Which cloth should we use? Is it cloth made of thick cotton or thin silk? Should the dishes possess large mass or small mass? Is it better to pull the cloth with a large force or pull it with a gentle and steady force?

Give scientific reasons for the following statements: To rectify the defect of far-sightedness or hypermetropia, convex lens of suitable focal length is used as corrective lens.

An electrician has to repair an electric fault on a pole of height 5m. She needs to reach a point 1.3m below the top of the pole to undertake the repair work (see the given figure). What should be the length of the ladder that she should use which, when inclined at an angle of 60^(@) to teh horizontal, would enable her to reach the required position? Also, how far from the foot of the pole shoudl she place the foot of the ladder? (you may take sqrt3= 1.73 )