PAGE: SC – RLT – A – 05
1.
OPTICAL CENTRE
2.
A concave lens has a virtual focus.
3.
The position of the image is:
4.
The height of the image formed is 1 cm.
5.
Position of the object:
between the first principal focus ( F1 ) and the Optical centre (O).
6.
Position of the object:
between the first centre of curvature ( C1 ) and the first principal
7.
Position of the object:
beyond the first centre of curvature ( C1 ).
8.
Nature of the lens is DIVERGING.
at the second centre of curvature ( C2 ).
focus ( F1 ).
9.
Type of image
Type of lens
(i)
an inverted magnified image
Convex lens
( ii )
an erect magnified image
Convex lens
( iii )
an inverted diminished image
Convex lens
10.
Position of the object:
11.
(DIAG)
between the first principle focus ( F1 ) and the Optical centre (O).
In a convex lens, a light ray parallel to the principal axis passes through the second principal focus (F 2) of the lens after
refraction.
Therefore, a beam of parallel light rays converges at the second principal focus.
So, a convex lens is called a converging lens.
12.
(DIAG)
In a concave lens, a light ray parallel to the principal axis appears to be coming from the first virtual principal focus of
the lens after refraction.
Therefore, a beam of parallel light rays appear to be diverging from the first virtual principal focus.
So, a concave lens is also called a diverging lens.
13.
(DIAG)
Ray diagram to show the formation of a real magnified image by a convex lens.
14.
Each lens is kept slightly over a printed paper, one by one.
The lens that forms a magnified erect image is
the convex lens.
The lens that forms a diminished erect image is the concave lens.
15.
(DIAG)
16.
(DIAG)
Characteristics of the image are:
Nature :
Virtual and Erect
Position :
On the same side of the lens with respect to the object
Size :
Magnified
17.
(DIAG)
18.
When the object is at a distance greater than 2f , the image is diminished.
When the object is at a distance of
2f , the image is of equal size.
When the object is at a distance less than 2f, the image is magnified.
When the object is at a distance of
f , the image is infinitely large.
Thus the size of the image increases and becomes infinitely large.
19.
The differences between a real image and a virtual image:
REAL IMAGE
1.
A
real
image
is
formed
VIRTUAL IMAGE
by
actual
1.
intersection of rays.
A
virtual
image
is
not
formed
intersection of rays.
2.
It can be obtained on a screen.
2.
It cannot be obtained on a screen.
3.
It is always inverted.
3.
It is always erect.
RAY DIAGRAM FOR REAL IMAGE FORMATION BY A CONVEX LENS:
RAY DIAGRAM FOR VIRTUAL IMAGE FORMATION BY A CONVEX LENS:
by
actual