Light- Reflection and Refraction
13. The horizontal line passing through
the centre of curvature and pole of the spherical mirror is known as Principal
axis.
14. The centre of curvature of a
spherical mirror is the centre of the hollow sphere of glass, of which the
spherical mirror is a part and usually represented by C.
15. The radius of curvature of a
spherical mirror is the radius of the hollow sphere of glass, of which the
spherical mirror is a part and usually represented by R.
16. The diameter of the reflecting
surface that is twice the radius is called its aperture.
17. Radius of curvature (R) = 2 focal length (f)
18.
Rules for ray
diagram-
i. The path of the reflected light ray
depends upon how the incident ray is oriented with respect to the principal
axis.
ii. A ray of light parallel to the
principal axis, after reflection pass through the principal focus.
iii. A ray of light passing through the principal focus of
a mirror becomes parallel to the principal axis of the mirror, on reflection
Position of object
|
Position
of image
|
Size
of image
|
Nature of image
|
At infinity
|
At focus F
|
Highly
diminished, point – sized
|
Real and inverted
|
Beyond C
|
Between F and
C
|
Diminished
|
Real and inverted
|
At C
|
At C
|
Same
size
|
Real and inverted
|
Between C and F
|
Beyond
C
|
Enlarge
|
|
At F
|
At
infinity
|
Highly
enlarged
|
Real and inverted
|
Between P and F
|
Behind
mirror
|
Enlarged
|
Virtual and erect
|
iv. A ray of light incident obliquely
towards the pole of mirror is reflected obliquely as per the laws of reflection
v. A ray of light passing through centre
of curvature of a mirror is reflected
back along the same path
22. Image formation by a concave mirror
for different positions of the object
23. Nature, position and relative size of
the image formed by a convex mirror:
Position of object
|
Position of image
|
Size of image
|
Nature of image
|
At infinity
|
At focus F behind the mirror
|
Highly
diminished, point
|
Virtual and erect
|
sized
|
|||
Between infinity and pole of the mirror
|
Between P and F behind the mirror
|
Diminished
|
Virtual and erect
|
24. The ratio of the height of the image
to the height of the object is known as the magnification.
25. Magnification is positive for virtual
image and negative for real image.
26. The phenomenon of change in the path
of light from one medium to another is called refraction of light.
27. The angle formed between the incident
ray and the normal is called angle of incidence and the angle formed between
the refracted ray and the normal is called angle of refraction.
28. The cause of refraction is the change
in the speed of light as it goes from one medium to another medium.
29. Larger the difference in speeds of
light, the greater will be the angle of bending and vice-versa.
30. When a ray of light passes from a
rarer medium to a denser medium, it bends towards the normal. Also, the angle
of incidence is greater than the angle of refraction.
