Last updated on February 9th, 2024 at 04:28 pm
CG Board Class 8 Science Refraction of Light Textbook Exercises which includes Fill in the blanks ,Question Answers and Extra Question and Answers from the Chapter.
Choose the correct alternative :-
(1) The refractive index of glass is…….
(a) 1.5 (b) 1.3 (c) 2.4 (d) 1.0
(2) The point from which a light ray passes without any deviation is
the-
(a) Focus
(b) Optical centre
(c) Focal length
(d) Centre of curvature.
(3) When light passes from one medium to another, it deviates from
its path. This is called :-
(a) Reflection of light
(b) Irregular reflection of light
(c) Refraction of light
(d) None of these
(4) When the object is placed at 2F. The image formed by a convex
lens will be at :-
(a) 2F
(b) F
(c) Between F and 2F
(d) Between F and optical centre.
Object placed at F -> On the side of the object
Object placed between F and 2F -> Beyond 2F
Object placed beyond 2F -> Between F and 2F
Object placed between F and Optical centre -> Beyond 2F
Q: What is a lens ? How many types of lens are there?
A lens is an optical device made of transparent material, often glass or plastic, with curved surfaces that can bend or refract light. There are two main types of lenses:
Convex Lens: This lens is thicker in the center and converges parallel light rays to a focal point. It is also called a converging lens.
Concave Lens: This lens is thinner in the center and diverges parallel light rays. It is known as a diverging lens.
Q: Define – (a) Principal axis (b) Optical centre (c) Focus
a. Principal Axis: The line joining the center of curvature of both the surfaces of the lens is called the principal axis.
b. Optical Centre: This is the center of the lens from which light rays pass without bending.
c. Focus:
In a convex lens, the point at which light rays parallel to the principal axis converge is called the principal focus.
In a concave lens, the point from which these light rays appear to diverge is also called the principal focus.
