Title Sci CH 10 Solutions file.pdf ✅

SCIENCE : LIGHT Å REFLECTION AND REFRACTION  CH—1 Shiv Das IMPORTANT EXAM-BASED QUESTIONS LIGHT, REFLECTION, SPHERICAL MIRRORS Short Answer Type Questions Q.1. What is light? What is the nature of light? Ans. Light is a form of energy which gives us the sensation of sight or vision. Nature of light: (i) Light is not visible to us. (ii) Light shows the phenomena of reflection, refraction and dispersion. (iii) Light is an electromagnetic wave which does not require a material medium for pro- pagation. Q.2. Name the two types of sources of light. Ans. Natural source of light: Sun, stars, moon, etc. Artificial source of light: bulb, tubelight, etc. Q.3. What is the speed of light in vacuum? Ans. It is 3 × 108 ms–1. Q.4. When light falls on a surface of an object, what will happen to it? Ans. It may be (i) absorbed (ii) transmitted or (iii) reflected. Q.5. Differentiate between a ray of light and a beam of light. Ans. A straight line path of light is called a ray of light whereas a bundle of such rays is called a beam of light. Q.6. Give an example of a reflector of light. Ans. A silver polished surface is the best reflector of light. Q.7. Name one means of communication provided by light. Ans. Optical fibres (called optical cable), which transmit many telephone messages at the same time. Q.1. What type of image is formed: (a) in a plane mirror (b) on a cinema screen? Ans. (a) Virtual image (b) Real image. Q.2. If the distance between an object and its image in a plane mirror is 5.6 cm, how far is the object from the mirror? Sol. The object is 5.6 2 = 2.8 cm from the mirror. Q.3. What is a spherical mirror? Ans. A spherical mirror is the mirror whose reflecting surface is a part of a hollow sphere. Q.4. What is the relationship between the focal length and radius of curvature of the spherical mirror? Ans. f (focal length) = R (radius) 2 Q.5. For what position of an object, a concave mirror forms a real image equal in size to the object? Ans. At C (centre of curvature). Q.6. For what position of an object, a concave mirror forms a virtual and magnified image? Ans. Between P and F (pole and focus). Q.7. If an object is placed at the focus of a concave mirror, where is the image formed? Ans. At infinity. Q.8. What should be the position of the object when a concave mirror is to be used: IMPORTANT EXAM-BASED QUESTIONS LIGHT, REFLECTION, SPHERICAL MIRRORS Short Answer Type Questions 10. LIGHT : REFLECTION AND REFRACTION
Shiv Das CH—2  SHIV DAS CBSE SECONDARY SERIES [X] (i) as a shaving mirror? (ii) as a doctor’s mirror? Ans. (i) Between P and F. (ii) Between P and F Q.9. What sign convention has been given to the focal length of: (a) a concave mirror? (b) a convex mirror? Ans. (a) Focal length of a concave mirror is –ve. (b) Focal length of a convex mirror is +ve. Q.10. What is the origin of all the distances measured in the spherical mirror? Ans. All distances are measured from the pole, i.e., the origin in the spherical mirror. Q.11. Give the sign convention of object distance in case of: (a) concave mirror (b) convex mirror Ans. (a) –ve (b) –ve Q.12. Give the Cartesian sign convention for: (a) Height of a real image. (b) Height of a virtual image. Ans. (a) –ve (b) +ve Q.13. A man standing in front of a spherical mirror finds his image having a very small head, a fat body and legs of normal size. What types of mirrors are used in these three parts? Ans. A very small head Æ Convex mirror A fat body Æ Concave mirror Legs of normal size Æ Plane mirror Q.14. What are the characteristics of the image obtained by a convex mirror? Ans. The image obtained by a convex mirror is always virtual, diminished and erect. Q.15. Can a plane mirror be called spherical mirror? Ans. Yes, a plane mirror can be called a spherical mirror of infinite radius. Q.16. What type of mirror is formed when a mercury drop falls on the earth? Ans. Convex mirror. Q.17. Give an application of diffused light. Ans. In a cinema hall, the screen is rough, thus the light falling on it gets scattered in all directions which enables every person sitting in the hall to see the picture on the screen. Q.18. If the radius of curvature of a concave mirror is 20 cm, what is its focal length? Sol. Radius of curvature, R = 20 cm \ f (focal length) = R 20 2 2 = = 10 cm. Q.19. Differentiate between virtual image of a concave mirror and of a convex mirror. Ans. The virtual image of a concave mirror is always magnified whereas the virtual image of a convex mirror is diminished. Q.20. What are the effects shown by light travelling in one medium falling on the surface of another medium. Ans. Following three effects are observed: (i) A portion of incident light is reflected back into the first medium. (ii) Some portion travels through the second medium along a changed path (refraction). (iii) The remaining part is absorbed by the second medium. Q.21. Differentiate between regular reflection and diffused reflection. Ans. This shows that object distance is always –ve.
SCIENCE : LIGHT Å REFLECTION AND REFRACTION  CH—3 Shiv Das When a parallel beam of light falls on a smooth surface, a parallel beam of reflected rays are produced. Such reflection shown by smooth surfaces is known as regular reflection. Q.22. What are fibre optic cables? Ans. Fibre optic cables. Fibre optic cables consist of thousands of glass fibres that transmit thousands of telephonic conversations at the same time over long distances. Q.23. Why is light considered to be an electro-magnetic wave? Ans. Light is considered to be an electro-magnetic wave because light waves do not require a material medium (like solid, liquid or gas) for their propagation. Q.24. The letter E is placed in front of a plane mirror: (a) How would its image look when seen in a mirror? (b) What is the name of the phenomenon involved? Ans. (a) (b) The phenomenon involved is lateral inversion. Q.25. Give some uses of a concave mirror. Ans. (i) It is used as a shaving mirror. (ii) It is used as reflectors in car head-lights. (iii) It is used by doctors as a head mirror. (iv) It is used in solar appliances to focus sunrays on the objects to be heated. Q.26. Show by ray diagram the formation of an image by a convex mirror. Ans. Image formed by a convex mirror is virtual, diminished, erect and behind the mirror between its P (pole) and F (focus) points. Q.27. Explain lateral inversion. Ans. If an object, which has two different sides, is placed in front of a plane mirror then right side of the object appears to be on the left side of the image and the left side of the object appears to be on the right side of the image. This change of side of an object and its mirror image is called lateral inversion. This phenomenon of lateral inversion occurs due to the reflection of light. Q.28. In what way is the word AMBULANCE printed in front of hospital vans? Why is it printed in this way? Ans. The word AMBULANCE on the hospital vans is written in the form of its mirror image as so that any person driving a vehicle ahead of the ambulance van, can see the laterally inverted alphabets correctly from his rear-view mirror and make way for it to pass through and enable it to reach the hospital quickly. When a parallel beam of light falls on a rough surface, the reflected light gets scattered. Such reflection shown by uneven or rough surfaces is known as diffused reflection or irregular reflection.
Shiv Das CH—4  SHIV DAS CBSE SECONDARY SERIES [X] (i) It is formed when reflected (or refracted) rays appear to meet when produced backward. (ii) It cannot be obtained on a screen. (iii) It is always erect. (iv) It is formed by concave, convex and plane mirrors. (v) It is formed by convex and concave lens. Long Answer Type Questions Q.25. Define reflection, incident light, reflected light, angle of incidence and angle of reflection. Ans. Reflection. The process of bouncing back of light rays, which fall on the surface of an object in the same medium, is called reflection. Incident light. Light which falls on the surface, is called incident light. Reflected light. Light which goes back after reflection, is called reflected light. Angle of incidence (–i). The angle between the incident ray and the normal, is called angle of incidence. Angle of reflection (–r). The angle between the reflected ray and the normal, is called angle of reflection. Q.26. Differentiate between real image and virtual image. Ans. Real image Virtual image (i) It is formed by the actual meeting of reflected (or refracted) rays. (ii) It can be obtained on the screen. (iii) It is always inverted. (iv) It is formed by concave mirror. (v) It is formed by convex lens. Q.38. Define the centre of curvature, radius of curvature, pole, principal axis of a spherical mirror and focus. Ans. Centre of curvature is the centre of the sphere of glass of which the mirror is a part e.g. C represents the centre of curvature. Radius of curvature is the radius of the sphere of glass of which the mirror is a part. The distance CP represents the radius of curvature. Pole. Middle part of the mirror is called pole. P represents pole, MP = M’P. Principal axis of a spherical mirror is the straight line joining the centre of curvature and pole of the mirror. Focus. The mid-point of CP is called focus (F). Q.39. Why does a concave mirror have a real principal focus?