Write down the relationship between relative refractive index and absolute refractive index. On which factors does the relative refractive index of a medium depend? [1 + 2]
OR
Show that if a monochromatic light ray passes symmetrically through an equilateral prism then the angle of deviation of that ray will be minimum
Relative refractive index of medium 2 with respect to medium 1:
1μ2 = μ2 / μ1
where μ2 and μ1 are absolute refractive indices of medium 2 and medium 1.
Factors on which relative refractive index depends:
OR
Let the angle of prism A = 60°.
For minimum deviation, the light ray passes symmetrically, i.e. angle
of incidence i = angle of emergence e.
So, angle of refraction r = A/2 = 30°.
Relation:
δmin = 2i – A
Since i = r when symmetrical,
i = A/2 + δmin/2.
Thus, δmin occurs when the ray passes symmetrically through the prism.
More WBBSE Easy level questions
Define dispersion of light. How would you identify monochromatic light and composite light with the help of a prism? [1 + 2]
Where is the image formed if the object is placed in between f and 2f of a convex lens ?
State whether the refractive index of a medium would increase or decrease if the angle of incidence is increased.
Whether a concave lens is called a converging or diverging lens? Answer with reason.
What is long-sightedness? What type of lens is used to remedy this defect? [2+1]
What is Hypermetropia? Which type of lens is used to rectify it? [2+1]
For the same angle of incidence, the angles of refraction in three different media A, B and C are 30°, 45° and 60° respectively. In which medium is the speed of light minimum and why? [3]
Write two causes of short-sightedness or myopia. Which type of lens is used to correct it? [2+1]
Write Snell's law of refraction of light. OR Write two characteristics of the image of an extended object formed when it is placed in between the optical centre and focus of a thin convex lens.
A ray parallel to the principal axis of a concave mirror follows which path after reflection by the concave mirror?
Write one use of a convex mirror
In the case of refraction of white light through a prism, the light of colour which deviates the least is yellow orange red violet
