Transcript Optics

Optics
Curved Mirror
Real or Virtual
1. A real image is formed by the intersection of light rays
from a pint of the object.
The image is always inverted and can be projected on a screen.
2. The term ‘virtual” is chosen to distinguish this type of image
from a “real” image, in which the rays do not pass through a
point of intersection
Object behind C
C
Image: Between C and F
Nature: Inverted, diminished, real.
F
(5) Object between F and the mirror
C
F
Try yourself !
Image: Behind the mirror
Nature: Erect, magnified, virtual.
Convex Mirror
F
Image: Behind the mirror
Nature: Erect, diminished, virtual.
C
Reversibility of light
(1) Object behind C
C
F
(3) Object between C and F
C
F
Try yourself !
1. A student uses a concave mirror to form a sharp
image of an illuminated object ‘P’ on a screen as
shown in the diagram below.
The distance between the object and
the mirror is found to be 0.5m
(a) What is the focal length of the
mirror?
(b) Explain your answer with the aid
of a ray diagram.
3. The letter “F” is put in front of a concave
mirror and the image is formed on a translucent
screen.
a. Looking at the screen from A, the image seen
is _______.
b. Looking at the screen from B, the image seen
is _______.
c. Looking into the mirror from B, the image seen
is ______.
2 The diagram below shows an experiment used to
find the focal length of a concave mirror.
a. Describe briefly how the experiment is performed?
b. Draw a ray diagram showing how an image is
formed in the above experiment.
c. If the distance between the mirror and the screen is
10cm, what is the focal length of the mirror?
Application of Curved Mirror
1. Convex Mirror
2. Concave Mirror
Convex Mirror
The image formed by a convex mirror is always :
1. erect
2. diminished
3. virtual
Convex Mirror
F
Image: Behind the mirror
Nature: Erect, diminished, virtual.
C
Convex Mirror
1. used in supermarkets to protect
against shoplifters.
Convex Mirror
2. used to help drivers see a
wider view at corners
Concave Mirror
The image formed by a convex mirror may be:
1. Erect & Magnified & Virtual
Or
2. Inverted & real
(magnified / diminished)
Object between F and the mirror
C
F
Try yourself !
Image: Behind the mirror
Nature: Erect, magnified, virtual.
Concave Mirror
1. make-up mirrors as
they give a magnified
image.
Image of the face is magnified
Concave Mirrors
2. Reflecting Telescope
the dim light from a distant star can be
collected and concentrated at the focus.
Distance Object
Parallel beam
C
Try yourself !
Image: At focus
F
Concave Mirrors
Object at F
Parallel beam
C
F
Try yourself !
Image: At infinity
Concave Mirrors
3. use as torches, car head lights
Concave Mirrors
3. Reflectors