CBSE Class 8 Science Collection of Assignments for 2014. Revision worksheets, Sample papers, Question banks and easy to learn study notes for all classes and subjects based on CBSE and CCE guidelines. Students and parents can download free a collection of all study material issued by various best schools in India. The study material has been carefully compiled by the best teachers in India. The students should practice the questions database to get better marks in examination. Please refer to other links for free download of high quality study material. Based on CBSE and CCE guidelines. Based on the same pattern as released by CBSE every year. Study material for final/ term/ SA1/ SA2 Examinations conducted by various schools affiliated to Central Board of Secondary Education (CBSE) in India and abroad. CBSE Study material has been compiled to help students preparation which will helps the students to concentrate more in areas which carry more marks.
2. Stars And The Solar System
3. Force and Pressure
2. Chemical Effects Of Electric Current
3. Some Natural Phenomena
1. Synthetic Fibres And Plastics
2. Materials: Metals and Non-metals
3. Pollution Of Air And Water (Pollution Of Air Only)
1. Pollution of Air and Water (pollution of water only)
2. Combustion and Flame
3. Coal and Petroleum
1. Crop Production and Management
2. Microorganisms: Friend and Foe
3. Conservation of Plants and Animals
1. Cell: Structure and Function
2. Reproduction in Animals
3. Reaching The Age of Adolescence
CHAPTER – LIGHT
* Light waves can travel through vacuum with a speed of 3x108 m/s.
* Light waves can pass through vacuum, sound waves cannot. Light waves are transverse waves while sound waves are longitudinal.
* When rays of light fall on smooth surface then bouncing back of light in the same medium in accordance with several laws is called reflection of light.
* A real image is formed when two or more reflected rays intersect each other at a point in front of the mirror. It can be obtained on a screen.
* A virtual image is formed when two or more reflected rays appear to intersect each other at a point behind the mirror. It can‘t be obtained on a screen
* The bending of light rays on passing from one medium to another is called refraction.
* Surface will behave as a smooth surface as long as the surface variations are small as compare to the wavelength of incident light. As wavelength of incident light is very small (4x10-7 m to 8x 10-7 m), therefore every surface (except mirror) acts as a rough surface & scattering of light or irregular reflection takes place.
* Any object in a room can be seen from all the parts of room because surface of the object is rough & it can scatter or reflect light in all directions.
* Laws of reflection are valid for all type of surfaces including spherical surfaces.
* Defects of eye
* Long Sightedness or Hypermetropia- Person suffering from this defect can see distant objects clearly but can‘t see near by object clearly. This defect is corrected by using convex lens
* Shortsightedness or Myopia- Person can‘t see distant objects clearly but can see near by object clearly. It can be corrected by using concave lens.
* Yellow spot- The area of best vision- Yellow spot or macula is a spot located in the centre at the back of eye. It contains maximum number of light sensitive cells. It is a region of colour vision and also the brightest vision.
* Blind spot- The area of no vision- Blind spot is the region of retina just below the yellow spot. Since there are no light receptors hence blind spot is the area of no vision.
* The least distance at which eye can see an object clearly is called near point of the eye. For normal eye it is 25 cm.
* The far point of the eye is the maximum distance at which eye can see clearly. For normal eye it is infinity.
Module – 1 & 2
(i) What makes things visible
(ii) Laws of Reflection
(iii) Regular and Diffused Reflection
(iv) Multiple Images
(vi) Dispersion of light
Assignment – 1
Q.1. Fill in the blanks:
(i) The study of light is known as _____________.
(ii) An image may be _____________ or _____________.
(iii) Image formed by plane mirror is always _____________ and _____________ and has the property of _____________.
(iv) Two parallel plane mirrors give rise to _____________ images.
(v) A normal eye can‘t see object closer than _________ cm.
Q.2. State True/False
(i) Light always travels in a straight line.
(ii) Most of materials show regular reflection when light strikes.
(iii) Spherical mirrors do not follow the laws of reflection.
(iv) A plane mirror image is called an upright image.
(v) A light ray never retraces its path.
(vi) The blind spot has no photo receptors.
(vii) An image formed at the retina of human eye leaves an impression for 1/10th of a minute.
Q.3. Give one word for the following:
(i) A perpendicular to the reflecting surface at the point of incidence.
(ii) The angle between reflected ray and normal.
(iii) The muscles which hold the eye lens in the human eye ball.
(iv) The defect of eye in which a person can see distant object clearly but not the nearby.
CBSE Class 8 Science Collection of Assignments for 2014
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