# CBSE – 10th Standard Science ## CBSE – 10th Standard Science

### Class 10 Question Bank Chapter 10 – Light – Reflection and Refraction

Qus 1. What makes things visible to us?

Ans. During the day, the sunlight helps us to make things visible to us.

Qus 2. What are the common phenomena associated with light?

Ans.The common phenomena associated with light are image formation by mirrors, the twinkling of stars, the beautiful colours of a rainbow etc.

Qus 3. What do you mean by diffraction of light?

Ans. If an opaque object on the path of light becomes very small, light has a tendency to bend around it and not walk in a straight line – an effect known as the diffraction of light.

Qus 4. Write the laws of reflection of light?

Ans.Laws of reflection of light are (i) The angle of incidence is equal to the angle of reflection, and (ii) The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane

Qus 5. What is the most used type of mirror?

Ans. The most commonly used type of curved mirror is the spherical mirror.

Qus 6. What are spherical mirrors?

Ans. The mirrors, whose reflecting surfaces are spherical, are called spherical mirrors.

Qus 7. What is convex mirror?

Ans. A spherical mirror whose reflecting surface is curved outwards, is called a convex mirror.

Qus 8. Explain the term ‘Pole’?

Ans. The centre of the reflecting surface of a spherical mirror is a point called the pole.

Qus 9. What is aperture?

Ans. The diameter of the reflecting surface of spherical mirror is called its aperture.

Qus 10. Write the uses of concave mirrors?

Ans. Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light..

Qus 11. Explain the uses of convex mirrors?

Ans. Convex mirrors are commonly used as rear-view (wing) mirrors in vehicles.

Qus 12. What do you mean by image distance?

Ans. The distance of the image from the pole of the mirror is called the image distance.

Qus 13. What is Reflection of light?

Ans. When travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as refraction of light.

Qus 14. What is refractive index?

Ans. The absolute refractive index of a medium is simply called its refractive index.

Qus 15. What is the SI unit of power?

Ans. The SI unit of power of a lens is ‘dioptre’.

Try these:-

• A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image.
• An object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.
• A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
• Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m s–1.
• The refractive index of diamond is 2.42. What is the meaning of this statement?