Important points of chapter: Refraction of light at Curved surfaces Chapter- 4 (SSC) syllabus
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Answer:
SPHERICAL REFRACTING SURFACE - DEFINITION
A refracting surface, which forms a part of a sphere of transparent refracting material, is called spherical refracting surface.
The two types are convex spherical refracting surfaces and concave spherical refracting surface.
Important Formulas in Chapter Refraction of Light at Curved Surfaces
The formula used when a light ray enters a medium with refractive index n2 from a medium with refractive index n1 at curved interface with a radius of curvature R is given as follows:
n2v−n1v=n2−n1R
The lens formula is given as
1f=1v−1u
where u is the object distance, f is the focal length of the lens and v is the image distance
The lens maker’s formula is given as
1f=(n−1)(1R1−1R2)
where n is the refractive index, R1 and R2 are radii of curvature and f is the focal length
In the next section, let us look at a few chapter questions to better understand the concepts discussed in the chapter.
Refraction of Light at Curved Surfaces Questions.
•How do you verify experimentally that the focal length of a convex lens is increased when it is kept in water?
•A double convex lens has two surfaces of equal radii ‘R’ and refractive index n = 15
•Find the focal length ‘f’.
•How do you appreciate the coincidence of the experimental facts with the results obtained by a ray diagram in terms of behaviour of images formed by lenses?
•Suppose you are inside the water in a swimming pool near an edge. A friend is standing on the edge. Do you find your friend taller or shorter than his usual height? Why?
•Find the refractive index of the glass which is a symmetrical converging lens if its focal length is equal to the radius of curvature of its surface.