## NCERT  Exemplar problems for Class 10 Science Chapter 10 Light Reflection and Refraction

Question 1. Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.
Answer. Due to variation in speed of light in different medium, light bends as it moves from One medium to another. Since, there are two surfaces for refraction which are parallel, the light ray should bend in opposite sense in them equally, the emerging light ray is always parallel to the incident ray.

Question 2. A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appears to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine. Support your answer with reason.
Answer. No, it will depend on the refractive index of the liquid in which the pencil is dipped. The tip at the bottom will get elevated as per the relation.

Question 3. Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is 1.5. Find out the absolute refractive index of diamond.

Question 4. A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object be placed in each case for obtaining these images?
Answer. Yes, for getting virtual image the object has to be placed between the optical centre and the focus. For real and enlarged image, the object should be placed between F and 2F.

Question 5. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will always be parallel to each other, whatever may be angle of incidence. Show the same with the help of diagram.
Answer. When the two mirrors are placed at 90 ° to each other, the incident and the reflected rays will remain parallel to each other.