CBSE | NCERT CLASS

 Class 8 Science : Light solution with question type answer for CBSE NCERT work sheet.  Light is a form of energy which helps us to see object around us. We see an object when light falls on them and reflected back  from it and reaches to our eye.  On basis of source of light, objects are two types of and they are are luminous object and non luminous object. Luminous object are those objects which can emit light. For example Sun, star, candle ,tube light ,bulb. Non luminous object are those objects which cannot emit light. For example book, pencil, chair, table. Another name of non luminous object is  illuminated object  because they get illuminated or light up by the light of luminous objects falling on them.  When a non luminous object can be seen? When  light from luminous object falls on non luminous object and reflected back to our eyes then we see the non luminous object. Reflection of light: The process of sending back light rays which fall on the surface of an object, is call

 Sound class 8 Chapter 13 science CBSE NCERT with solution worksheet. Sound is a form of energy which makes a perception of hearing. Sound is produced by vibrating objects. For example sound is produced by a vibrating bicycle Bell, sound is produced when a stretched rubber band vibrates,  sound is produced when a cheater string vibrates,  sound is produced when our vocal cords vibrate,  sound is produced when the ear column enclosed in a a tube vibrates. The human beings produce sound by using the voice box which is called larynx. The human voice box contains two ligaments known as vocal cords.  Sound is produced by the vibrations of vocal cords. The lungs pass a current of air between the two vocal cords. This year makes the vocal cords vibrate.  And the vibrating vocal cords produce sound.   Due to shorter vocal cords, the frequency of women's voice is higher than that of a man.  For this reason the woman's voice is comparatively shriller than man. Propagation of sound: the p

Cell: Structure and Function Brief History of Cell Discovery An English scientist, Robert Hooke, discover cell in 1665 . When he was examining a dried section of cork tree with his own made light microscope, he saw many honeycomb like empty chambers in it. He named each hollow space as cell. After his discovery of cell, considerable progress has been made in the development of powerful and more sophisticated microscopes. In 1831, Scottish scientist Robert Brown named nucleus of a cell. In 1839, Parkenje named Protoplasm . In 1839, Schleidon and Schwamm together announced cell theory -