What Makes Things Visible When light from an object enters our eyes, then we see the object. The light may have been emitted or reflected by the object. Mirror Highly polished surface is called mirror. Reflection Bending back of light ray after falling on a surface, is called reflection. Incident ray The light ray which strikes any surface, is called incident ray. Reflected ray The ray that comes back from the surface after reflection, is called as reflected ray. Normal Line perpendicular to surface at point of incidence of light ray, is called normal. Angle of incidence The angle between normal and incident ray, is called angle of incidence. Angle of reflection The angle between normal and reflected ray, is called angle of reflection. Laws of reflection (i) The incident ray, the normal at the point of incidence and the reflected ray, all lie in the same plane. (ii) The angle of incidence is always equal to ...
Reaching the Age of Adolescene Adolescene The period of life, when the body undergoes changes , leading to reproductive maturity, is called adolescene. Period - age of 11 to age of 19. Also called " teen age ". Because this period covers the teen ages i.e, 13 to 19 Adolescene may begin earlier in girls than boys. Puberty Period during adolescene, when human body undergoes several changes, is called puberty. Important change - Boys and girls become capable of reproduction. Changes at puberty Increase in height Change in body shape Change in voice Increased activity of sweat and sebaceous glands Development of sex organs Reaching mental, intellectual and emotional maturity Changes in Girls Increase in height Region below the waist becomes wider Less growth of muscles Voice becomes high pitched. Increased activity of sweat and sebaceous glands Ovaries enlarge. Eggs begin to mature....
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