Lakhmir Singh Physics Class 10 Solutions Page No:229
Question 29: The following table gives the refractive indices of a few media :
Use this table to give an example of :
(i) a medium pair so that light speeds up when it goes from one of these medium to another.
(ii) a medium pair so that light slows down when it goes from one of these medium to another.
(i) Crown glass to water.
(ii) Water to diamond.
Question 30: Refractive indices of four media A, B, C and D are given below :
In which of these four media is the speed of light (i) maximum, and (ii) minimum ?
(i) A (It has least refractive index).
(ii) D (It has highest refractive index).
Lakhmir Singh Physics Class 10 Solutions Page No:239
Question 1: Name the lens which can concentrate sun’s rays to a point and burn a hole in a piece of paper.
Solution : Converging lens.
Question 2: Give the usual name for the following :
A point inside a lens through which the light passes undeviated.
Solution : Optical center.
Question 3: A 1 cm high object is placed at a distance of 2ƒ from a convex lens. What is the height of the image formed ?
Solution : 1 cm (same as the height of the object).
Question 4: If the image formed by a convex lens is of the same size as that of the object, what is the position of the image with respect to the lens ?
Solution : At 2F (At twice the focal length).
Question 5: If an object is placed at the focus of a convex lens, where is the image formed ?
Solution : The image is formed at infinity (at very large distance).
Question 6: Where should an object be placed in order to use a convex lens as a magnifying glass ?
Solution : Object should be placed at a distance less than focal length.
Question 7: Where should an object be placed in front of a convex lens so as to obtain its virtual, erect and magnified image ?
Solution : The object should be placed within focus.
Question 8: Where should an object be placed in front of a convex lens so as to obtain its real, inverted and magnified image ?
Solution : Object should be placed between f and 2f.