Page 137 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

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15 Light

Chapter in a Nutshell

v Light is a form of energy which helps us see things.
v Light always travels in a straight line. This property of light is known as rectilinear propagation
of light.

v The direction or path along which the light energy travels in a medium is called a ray of light.
v A group of light rays is called a beam of light.

v The measurement of intensity or brightness of the light is termed as luminous intensity of
light.

v The bouncing back of light from the mirror into the same medium is called reflection of
light.

v There are some important terms related to reflection of light–incident ray, point of incidence,
normal, reflected ray, angle of incidence and angle of reflection.
v Reflection of light always follows laws of reflection.

v There are two laws of reflection:
(a) The incident ray, the reflected ray & the normal at the point of incidence, all lie in the

same plane.
(b) The angle of incidence & angle of reflection are always equal. i.e., ∠i = ∠r.

v Reflection may be of two types–regular and irregular.
v Image is the exact copy of the object in the mirror.

v Images are of two types–real & virtual.
v The interchange of the left & right in an object & its image is called the lateral inversion.
v A spherical mirror is a mirror cut out of a reflective sphere. It is of two types–concave and

convex.
v A concave mirror, also known as the converging mirror, is a spherical mirror in which the

reflection of light takes place at the inner surface.
v A convex mirror, also known as the diverging mirror, is a spherical mirror in which reflection

of light takes place at the outer surface.
v Images formed by spherical mirrors can be conveniently shown by same geometric diagrams

called ray diagrams.
v A lens is a transparent material bound by two curved surfaces. It is of two types– concave &
convex.

v A convex lens is thicker in the middle while a concave lens is thicker at the edges.

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