1. by JSC NAREN VII B

2. SL NO TOPIC 1LIGHT TRAVELS IN A STRAIGHT LINE 2REFLECTION OF LIGHT 3RIGHT OR LEFT 4PIN HOLE CAMERA 5CONCAVE SPHERICAL MIRROR 6CONVEX SPHERICAL MIRROR

3.  In a homogenous transparent medium light travels in a straight line and this is known as rectilinear propagation of light. This can be demonstrated by the following experiment:  Now slightly displace any one of the cardboards and try to see the flame through the pinhole of the cardboard C. The flame will not be visible. From this it is clear that light travels in a straight line.

4.  Reflection is the change in direction of a Incident Ray at an interface of a mirror so that Incident Ray reflects into the medium from which it originated.  This induced change of direction in light by a mirror is called reflection of light. Reflected light is called as Reflected Ray.

5.  If somebody is standing in front of a mirror and observes his image, it will be found that the ‘right’ appears ‘left’ and the ‘left’ appears ‘right’ as shown in the following figure.  Only sides are interchanged; the image does not appear upside down.

6.  A pinhole camera is a simple camera without a lens and with a single small aperture — effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box. The human eye in bright light acts similarly, as do cameras using small apertures.  The image appears on screen is not an erect image and thus appears as inverted image.

7.  If a person standing in front of a concave spherical mirror, observes his image, from a distance greater than that of centre of curvature, the image is not erect but upside down and it is smaller than the original object.

8.  Similarly for persons standing in front of a concave spherical mirror, at centre of curvature and between centre of curvature and focal point, the images are not erect but upside down.

9.  Using a ray parallel to the principal axis and one incident upon the centre of the mirror, the position of the image can be constructed by back-projecting the rays which reflect from the mirror. The virtual image that is formed will appear smaller and closer to the mirror than the object.