Understand basic concept of light and properties
- 2. Light What makes things visible :- Light helps us to see objects. We cannot see objects in the dark . An object becomes visible when light emitted or reflected by it reaches our eyes.
- 3. 2) Reflection of light :-When light falls on a polished or shiny surface it changes its direction. This is called reflection of light..
- 4. Incident Ray - The light ray, which strikes any surface, is called the incident ray. Reflected Ray - The ray that comes back from the surface after reflection is known as the reflected ray Normal - The perpendicular line drawn at the point of incidence is called normal. Angle of Incidence The angle between the normal and incident ray is called angle of incidence (∠i). Angle of Reflection The angle between the normal and reflected ray is called angle of reflection (∠r). The angle of incidence is always equal to the angle of reflection
- 5. Laws of reflection of light - 1) Angle of incidence is always equal to the angle of reflection. 2) The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.
- 6. Image formed by a plane mirror i) The image is vertical ii) The image is same size as the object iii) The image is at the same distance from the mirror as the object is in front of it. i) The image is virtual (cannot be obtained on a screen). i) The image is laterally inverted.
- 7. Regular and Diffused Reflection Regular Reflection Reflection from a smooth surface like a mirror that follows the laws of reflection is called a regular reflection When parallel rays of light fall on a smooth surface, the reflected rays are parallel. This is called regular reflection. Regular reflection forms images of objects.
- 8. Diffused Reflection Reflection over a surface that has irregularities where it does not follow the laws of reflection is called an irregular or diffused reflection. When parallel rays of light fall on a rough surface, the reflected rays are not parallel. This is called diffused or irregular reflection. Diffused reflection does not form images of objects.
- 9. Multiple images :- When two mirrors are kept inclined at an angle, they can together form multiple images. This is because the image formed by one mirror forms the object for the other mirror.
- 10. Kaleidoscope :- A kaleidoscope is a device used to see multiple images of objects. It has three inclined mirrors at an angle of 60° to each other. This arrangement is usually kept in a cylindrical box and has a few pieces of coloured glasses kept at one end . We can see beautiful patterns and designs due to multiple images formed by the mirrors.
- 11. Dispersion of light :- Sunlight or white light is a mixture of seven colors. The splitting up of sunlight or white light into its colors is called dispersion of light . When a beam of sunlight is passed through a glass prism it is split up into the seven rainbow colors. The colours are violet, indigo, blue, green, yellow, orange and red (VIBGYOR) Rainbow is caused due to the dispersion of sunlight by water drops in the atmosphere. by the mirrors.