Viva Voice Questions With Answer
Refractive Index of Liquid – Practical Exam
For: Science Class 11 | Physics

Q.1: What is refractive index of a transparent medium?
Ans. The ratio of the velocity of light in vacuum to the velocity of light in the given medium.
n = C / V = Sin i / Sin υ
Where c = velocity of light in the vacuum, v = velocity of light in the given medium.

Q.2: What are the factors affecting the refractive index?
Ans. (a) Wave length of the light used. (b) Nature or the medium.

Q.3: What is meant by monochromatic light?
Ans. Light consisting of only one colour or wave-length.

Q.4: Can you see all the wave-lengths?
Ans. No, wave lengths from 4000Ao (violet) to 6000 Ao (Red) are visible only.

Q.5: Can the refractive index of a medium be less than or equal to 1?
Ans. No, since in the relation: n = C / v and we always have: V < C, n > 1

Q.6: What is the refractive index of? (a) glass (b) water (c) air (d) vacuum
Ans. (a) 1.5 (b) 1.33 (c) 1.003 (d) (V = C in vacuum)

Q.7: What is the principle of this experiment?
Ans. The focal length (f) of combination of thin lenses is given by: 1/ f = 1 /fl + 1/fg
Where, fl and fg are the focal lengths, the liquid lens, and the glass lens respectively.

Q.8: What type of lens is formed by water?
Ans. Plano-concave lens.

Q.9: What type of combined lens is formed?
Ans. Plano-concave lens.

Q.10: Which one is greater, the focal length of the combination or the focal length of the convex lens?
Ans. The focal length of the combination.

Q.11: What is function of plane mirror?
Ans. To reflect the rays refracted by the lens of liquid. When the pin is at the centre of curvature of the combination, the reflected rays form the image at the position of the pin.

Q.12: What are the laws of reflection?
Ans. (a) The angle of incidence is always equal to the angle of reflection. (b) The angle of incidence, angle of refraction and the normal to the point of incidence, all lie in one plane.

Q.13: What are laws of refraction?
Ans. (a) The ratio Sin i / Sin r is always constant give a given medium and is called refracted index,μ or n (Snell’s Law). (b) The incident ray, the refracted ray and normal to the point of incidence, all lie in the same plane.

Q.14: Which substance has greatest value of refractive index?
Ans. Diamond (2.42)

Q.15: What defect may be produced in the image when very small quantity of water and hence the image produced will be distorted.
Ans. The water surface will not be flat due to the small quantity of water and hence the image
produced will be distorted.