Page 7 - 10-phy-12 Geometrical Optics
P. 7
Eye
A Clamp
Needle
D
h1 Stand
h2
Concave Mirror
O
Ring
Fig. 12.2.2
Materials Concave mirror, sharp pointed parallax needle, metre rule, iron stand with retort ring,
Required split corks or needle holders, plumb line, water
Procedure
1. Clean the concave mirror with cotton cloth.
2. Obtain a clear and distinct image of a distant object on a screen/wall.
Measure the distance between screen and mirror. This is approximate
focal length of the concave mirror.
3. Place the concave mirror on the retort ring such that its principal axis is
vertical.
4. Clamp the parallax needle horizontally above the mirror at a distance
about twice the approximate focal length.
5. By viewing from the top of the needle adjust the position of needle to
remove the parallax between the tip of the needle and the inverted image.
(In this position, both the tips remain coincident at the center of
curvature C regardless of the movement of the
eye).
6. Measure the distance OA = h1 between the tip
of the needle 'A' to the center (pole) of the
mirror 'O' using plumb line. What happens to the
7. Put a few drops of water on the mirror to form a image by pouring
water on the mirror?
thin layer of water on the surface of mirror.
9
A Clamp
Needle
D
h1 Stand
h2
Concave Mirror
O
Ring
Fig. 12.2.2
Materials Concave mirror, sharp pointed parallax needle, metre rule, iron stand with retort ring,
Required split corks or needle holders, plumb line, water
Procedure
1. Clean the concave mirror with cotton cloth.
2. Obtain a clear and distinct image of a distant object on a screen/wall.
Measure the distance between screen and mirror. This is approximate
focal length of the concave mirror.
3. Place the concave mirror on the retort ring such that its principal axis is
vertical.
4. Clamp the parallax needle horizontally above the mirror at a distance
about twice the approximate focal length.
5. By viewing from the top of the needle adjust the position of needle to
remove the parallax between the tip of the needle and the inverted image.
(In this position, both the tips remain coincident at the center of
curvature C regardless of the movement of the
eye).
6. Measure the distance OA = h1 between the tip
of the needle 'A' to the center (pole) of the
mirror 'O' using plumb line. What happens to the
7. Put a few drops of water on the mirror to form a image by pouring
water on the mirror?
thin layer of water on the surface of mirror.
9
