Spherical mirrors/terms Flashcards
What do plain mirrors dont and spherical ones do? why do we need spherical mirrors?
Plain ones do not converge or diverge parallel beams of light but spherical ones do
define spherical mirrors
mirror whose reflecting surface is a part of a hollow sphere of glass
types of spherical mirrors
concave nd convex
concave mirrors definition
the mirrors in which reflection of light takes place in the bent in surface. ex - inner side of the steel spoon the back surface is covered in paint
convex mirror definition
wherein reflection of light takes place in the bulging out surface. ex - back side of steel spoon
IMPORTANT TERMS 1) center of curvature
the center of the hollow sphere of glass of which the mirror is a part, denoted by ‘C’! DRAW THE DIAGRAM DIYA
Pointers related to the center of curvature
not a part of the mirror, lies outside the reflecting surface, CONCAVE -> INFRNT, CONVEX -> BEHIND
2) Radius of curvature
Radius of the hollow sphere of glass of which the mirror is a part! Centre to Pole, denoted by ‘R’
3) Pole
center of the sperical mirror, middle point of the mirror, denoted by ‘P’, lies on the surface of the mirror
4) Principal Axis
The straight line passing thru the center of curvature and pole of the mirror, passes thru C and P, It is perpendicular (normal) to the mirror @ the pole!
Aperture of the mirror
the portion from which reflection takes place, reprsntd by the diametr of the reflecting surface, shows the size of the mirror, IT IJNT A LINE IT IJ A DISTANCE
CONCAVE MIRRORS PRINCIPAL FOCUS
A point on the principal axis on which all the rays parralel to the principal axis converge after reflection (DIAGRAM DIYA), it is real, in the front of the mirror
CONCAVE MIRRORS FOCAL LENGTH
dist b/w pole and principal focus, denoted by ‘f’
Explain how to get the image of the sun using a concave mirror
FIRSTLY, Sun is at a far dist -> rays are parallel
SECONDLY, image of the sun can be produced at the focus of the mirror
ISTEPS -
1) take a mirror and point it at the sun, hold up a paper infrnt of the mirror such that the reflected rays fall on it
2) A small patch of bright light will appear on the paper, adjust to obtain the brightest point -> IMAGE O THE SUN
3) it is formed at the ‘focus’
NOTES - A few more mins and ppr will start burning -> HOLE
bcs concave mirror CONVERGES -> the heat energy ->screen
focal length of our mirror is the approx dist b/w paper (image) and mirror
CONVEX MIRRORS PRINCIPAL FOCUS
a point on the principal axis from which a eam of light rays initially parallel to the principal axis appear to diverge after reflection from a convex mirror
what is so unique about the focus of a convex mirror/
That the relfected rays do not actually pass through the focus, they appear to hence it is a virtual focus behind the mirror
Focal length of a convex mirror
it is the dist b/w the focus and pole (bbehind the mirror)
FACTOID - How much is the focal length of a plane mirror y?
it is infinite bcs it doesn’t converge or diverge
Explain the relationship b/w ‘f’ and ‘R’
Radius is dist frm centre of curvature to pole, Principal Focus (F) is the mid point of ‘R’ (bcs it lies mid way b/w CENTRE and Pole) , Focal length (f) is
from Principal focus to pole -> ‘f’ is half of ‘R’ -> f = R/2 or R = 2F
