Q: What do you mean by refractive index of mirror?
Ans: When light passes from one medium to another medium then the constant sin I / sin r is called the refractive index of the second medium with respect to the first medium.
Q: What do you mean by total internal reflection?
Ans: When light passes from denser medium to the rarer medium by increasing angle of incidence (i),the angle of refraction also increases in such a way that ( r) is always greater than 1 till for a particular value of angle of incidence the corresponding angle of refraction becomes 900 and the refracted ray grazes along the surface. If angle of incident increases more then refracted ray comes back to the denser medium. This is called total internal reflection.
Q: What do you mean by critical angle?
Ans: The angle of incidence in the denser medium for which corresponding angle of refraction is 900 in the rarer medium is called the critical angle. This angle of incidence is denoted by C.
Q: Write two conditions of total internal reflection.
Ans:
1. The ray of light should travel from a denser medium to a rare medium.
2. The angle of incidence should be greater than the critical angle.
Q: State laws of reflection.
Ans: There are two laws of refraction.
1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, the reflected ray and normal at the point of incidence, all lie in the same
plane.
Q: What is difference between the primary and secondary Rainbow.
Ans: The main difference is that in primary rainbow total internal refection occurs only one time but for the secondary rainbow it occurs two times and its colours are faint.
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