7 Science Chapter 15 Light

Chapter Notes and Summary
• Light is a form of electromagnetic radiation (radiation energy) which produces in us sensation of vision.
• Light travels along straight line.
• A highly polished or shiny surface, such as mirror reflects most of light falling on it.
Reflection of light : A mirror or shiny surface that acts as mirror, changes direction of light that falls on it. This change in direction of light by a mirror is called reflection of light.
Spherical mirrors : surface of a mirror or a shining spoon could be considered as a curved mirror. most commonly used type of curved mirror is spherical mirror. reflecting surface of such mirrors can be considered to form a part of surface a sphere. Such mirrors, whose reflecting surfaces are spherical are called spherical mirrors.
• surface of water (clear fresh water) can also act like a mirror and change path of light.
Image (optical) : An optical appearance produced by light or other radiations from an object reflected in mirror on refracted through a lens is called image.
• Convex mirror always forms virtual images which are erect and smaller in size than object. However, convex mirrors form images of objects spread over a large area.
• Doctors use concave mirrors for examining eyes, ears, nose, throast and teeth. These are also used as reflectors of torches, head lights of cars etc. Convex mirrors are used as side mirrors in cars etc.
• Lenses are also used to form images. Convex lenses are thicker in middle than at edges. On other hand, concave lenses are thinner in middle than at edges.
• A concave lens always forms erect, virtual and diminished image. It is called diverging lens because it diverges light falling on it.
• Convex lenses can form both real and virtual images depending upon position of object. These give magnified images when objects are very near lens. A convex lens is called converging lens as it converges light falling on it.
• White light splits into seven colours when it enters a prism. e.g., violet, indigo, blue, green, yellow, orange and
red. This phenomenon is called dispersion of light.

Leave a Reply

Your email address will not be published. Required fields are marked *