Class - 10
Science - Physics
Chapter :- 9
Light - Reflection and Refraction
Notes
Reflection :- The bouncing back of light when strikes on a polished surface is called Reflection of Light.
Refraction :- The
change in the direction of light ray when passing from one medium to another is
called Refraction of Light.
Refraction
causes due to the change in the speed of light.
Principal Axis :- The
line joining the Pole (P) and Center of Curvature (C).
Pole (P) :- The center of spherical mirror.
Centre of Curvature (C) :- The Center of a
hollow glass sphere of which the mirror a part.
Focal Length (f) :-
The distance between the Pole (P) and the Focus (F).
Optical Center (O) :- The
point on a lens through which a ray of light passes without diviation.
Relation between Focal length (f) and Radius of curvature (R):
f
= R/2 or R = 2f
Formulas related to
Mirror :-
·
Mirror Formula :-
1/f = 1/v + 1/u
·
Magnification (m) :-
m = h’/h = -v/u
Rules to Form image by
Concave Mirror :-
- A ray of
light going parallel to Principal Axis, after reflection it will pass through
Principal Focus (F).
- A ray of light passing through the Principal
Focus (F), after reflection it will become parallel to Principal Axis.
- A ray of light passing from Center of Curvature
(C), after reflection it will go back along the same path.
Rules to Form image by
Convex Mirror :-
- A ray of
light going parallel to Principal Axis, after reflection it will appear to
diverge from Principal Focus (F).
- A ray of light appears to going towards the
direction of Principal Focus (F), after reflection it will become parallel to
the Principal Axis.
- A ray of light appears to going in the direction
of Center of Curvature (C), after reflection it will go back along the same
path.
Formulas related to Lens
:-
·
Lens Formula :-
1/f = 1/v – 1/u
·
Magnification (m) :-
m = h’/h = v/u
·
Power of Lens (P) :-
P = 1/f
Rules to Form image by
Convex Lens :-
- A ray of
light parallel to the Principal Axis, after refraction it will passes through
Principal Focus (F2).
- A ray of light passing through a Principal Focus
(F1), after refraction will emerge parallel to the Principal Axis.
- A ray of light passing through the Optical Center (O), after refraction will pass without any bend or deviation.
Rules to Form image by
Concave Lens :-
- A ray of
light parallel to the Principal Axis, after refraction the ray appears to
diverge from Principal Focus (F1).
- A ray of light appearing to meet Principal Focus
(F2), after refraction will emerge parallel to the Principal Axis.
- A ray of light passing through the Optical Centre (O), after refraction will emerge without any bend or deviation.
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