David Bangaru

9. REFLECTION OF LIGHT points to remember : 1. Transmission of light : Light coming out from a source spreads in all directions. Light is transmitted in a straight line. 2. Reflection of light : The turning back of the rays of light after falling on a surface is called the reflection of light. 3. Image formed in a plane mirror : The image formed in a plane mirror is upright, laterally inverted, of the same size as the object and as far behind the mirror as the object is in front of the mirror. 4. Laws of reflection of light : (1) The incident ray, the reflected ray and the normal to the reflecting surface at the point of incidence are in the same plane. (2) The incident ray and the reflected ray are on the opposite sides of the normal. (3) The angle of incidence and the angle of reflection are of equal measure. 5. Types of reflection of light : Regular reflection and irregular reflection are the two types of reflection. If the reflecting surface

Important points to remember : 1. There are microorganisms around us. Some of these produce diseases and cause harm to us. They enter our body through food, water or air. Those who have weak resistance power get the disease and develop the symptoms of the disease. 2. When a person gets a disease, his physical and mental condition and overall health are affected. 3. Types of diseases : On the basis of their mode of spreading, diseases are classified into : (1) epidemic diseases (2) communicable diseases and (3) contagious diseases. Microorganisms like bacteria and viruses cause diseases. (1) Epidemic diseases : Changes in the weather or contamination of water can cause infection of disease to many people to get the same disease at the same time. Such diseases are called epidemic diseases. Cholera, typhoid, influenza (flu), diarrhoea, conjunctivitis are epidemic diseases. (2) Communicable diseases : Diseases which are spread through air by germs in t