Question

a] Draw a ray diagram to show the path of a light ray passing from one medium to another, if two media are optically exactly the same
b] Absolute refractive indices of medium 1 and medium 2 are n1 and n2 respectively. What is the refractive index of medium 2 with respect to medium 1?
c] How does the velocity of light vary with the change in optical density of the media?

Answer 1

a) up

b) n12(read as n of 1 w.r.t.2)=v2/v1=(f.Lambda2)/(f.Lambda 1)=(Lambda2)/(Lambda1)=sin i/sin r. Here f is frequency of light which remains constant due to law of conservation of energy. Here, i is angle of incidence formed at interface in medium 2 and r is angle of refraction in madium 1.

According to Snell’s law n2sin i=n1 sin r. Therefore sin i/sin r=n1/n2 or n12=ni/n2. Here, n1 and n2 are absolute refractive indices of medium 1 and 2. Absolute refractive index means refractive index w.r.t. air or vacuum.

c)Velocity of light depends on the density of medium. More the optical density of a medium less is the speed of light and less is the optical density of medium more is the speed of light.