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Refraction of light covers definition, laws of refraction of light with diagram, notes for class 8,9,10 Refraction : The change in direction of the path of light, when it passes from one transparent medium to another transparent medium, is called refraction. Refraction of light is essentially a surface phenomenon.    You may Like NCERT Solutions MCQ Questions and Answers Why is refraction occurred? Because when light travels from a optical optical medium to another optical medium its speed changes and due to changing in speed it is direction is also changes. Because of this refraction occurred.  When a Ray of light travelling in one transparent medium strikes obliquely at the surface of another transparent medium, a part of light comes back to the same medium obeying the laws of reflection and is called the reflected light.  The remaining part of the light passes Into the other medium and travels in a straight path different from its initial direction and is called reflected light.  Op

Parallelogram : a quadrilateral is called a parallelogram if both pairs of its opposite sides are parallel. Rhombus : a parallelogram having all sides equal is called a rhombus. Rectangle : a parallelogram in which each angle is a right angle is called a rectangle. Square : parallelogram in which all the sides are equal and each angle measures 90 degree is called a square. Trapezium : a quadrilateral having exactly one pair of parallel sides is called a trapezium. Isosceles trapezium : a Trapezium whose non parallel sides are equal is called an isosceles trapezium. Kite : a quadrilateral is called a kite if it has two pairs of equal adjacent sides but unequal opposite sides. 1. Question PQRS is a parallelogram. In PQRS parallelogram angle P = 105°. Find the measure of each of the angles Q, R and S. Answer Since the sum of any two adjacent angles of a parallelogram is 180°, ∠P + ∠Q = 180° 105° + ∠Q = 180° ∠Q = (180° - 105°) = 75° Also, ∠P = ∠R   [  opposite angles of parallelogram are e

  Linear equation : The equation in which one variable present and highest degree is 1 is called linear equation in one variable.  Equation : An equation is a statement of equality of two algebraic expressions involving one or more   unknown quantities, called variables.    Rules   for solving a linear equation: i)  we can at the same number on both sides of the equation ii)  we can subtract the same number from both sides of the equation iii)  we can multiply both sides of the equation by the same non zero number iv)  we can divide both sides of the equation by the same non zero number. 1)  two numbers are in the ratio 5 : 4. Is the sum of the numbers is 207,find the numbers. 2) 3/4  of are number is 10 less than the original.  Find the number.  3) Five-sixth of a number is 20 more than three-fourths of the number. Find the number.  4) Thirty  is divided into two parts such that 6 times of the first part added to 2 4 times the second part makes 140. Find the numbers.  5) Find the numb

 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 Science MCQ Solution for CBSE NCERT students. 1. Question Voice of which of the following is likely to have the minimum frequency? A. baby girl B. baby boy C. a man D. a woman Answer The voice of man has the least frequency. You may Like   1. MCQ Questions for  Class 8 Maths with Answers Download PDF Solution Chapter Wise 2. MCQ Questions for Class 8 Science Chapter 6 Combustion and Flame with Answers  3. MCQ Questions for Class 8 Science Chapter 14 Chemical Effects of Electric Current with Answers 2. Question Sound can travel through: A. gases only B. solids only C. liquids only D. solids, liquids and gases Answer Sound does not need any material medium to travel. 3. Question Which of the following vibrates when a musical note is produced by the cymbals in an orchestra? A. stretched strings B. stretched membranes C. metal plates D. air columns Answer Metal plates vibrates when a musical note is produced by the cymbals in an orchestra. 4. Question A musical instrument

 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

  1. Question Find the volume, lateral surface area and the total surface area of the cuboid whose dimensions are: (i) length = 22 cm, breadth = 12 cm and height = 7.5 cm Answer (i) We know that, Volume of cuboid = Length × Breadth × Height = (22 × 12 × 7.5) = 1980 cm3 We also know that, Total Surface Area of cuboid = 2 (lb + bh + hl) = 2 (22 × 12) + (22 × 7.5) + (12 × 7.5) = 2 (264 + 165 + 90) = 1038 cm² Now, Lateral surface area of cuboid = [2 (l + b) × h] = [2 (22 + 12) × 7.5] = 510 cm² (ii) length = 15 m, breadth = 6 m and height = 9 dm Answer: We know that, Volume of cuboid = Length × Breadth × Height = (15 × 6 × 0.9) = 81 m³ Total Surface Area of cuboid = 2 (lb + bh + hl) = 2 (15 × 6) + (15 × 0.9) + (6 × 0.9) = 2 (90 + 13.5 + 5.4) = 217.8 m² Lateral surface area of cuboid = [2 (l + b) × h] = 2 (15 + 6) × 0.9 = 37.8 m² (iii) length = 24 m, breadth = 25 cm and height = 6 m Answer: Volume of cuboid = Length × Breadth × Height = (24 × 0.25 × 6) = 36 m³ Total Surface Area of cuboid =

  The   surface area   is the   area   that describes the material that will be used to cover a geometric   solid . When we determine the   surface areas   of a geometric   solid   we take the sum of the   area   for each geometric form within the   solid . The   volume   is a measure of how much a figure can hold and is measured in cubic units. The  bodies that have a definite shape and volume are called solids.  The space occupied by a solid body is called its volume.   solid bodies occur in solid bodies occur in various shapes such as cuboids cubes cylinder cones and spheres.  Cuboid:  a solid bounded by six rectangular plane faces is called a cuboid.  Example: a matchbox, chalk box, a brick, a title,  a book. Cuboid has 6 rectangular faces, 12 edges, 8 vertices.   any face of any face of a cuboid maybe called its base.   the four faces which meet the base are the four faces which meet the base are called lateral faces of the cuboid.   6 faces are ABCD, EFGH,  EFBA, HGCD, EHDA, FGCB

 Chemical effect of electric current: part 2 25. Sugar solution does or does not conduct electricity. Answer: sugar solution does not conduct electricity. 26. A torch bulb cannot be used to detect weak electric current flowing through a liquid in a circuit .............why? Answer: the current in the circuit may be weak if the the electrical conductivity of the liquid we are testing is very low. So, if we test a liquid hav*ZzzZing very low electrical conductivityz by using a torch bulb in the circuit , then the bulb may not glow at all. Because too week current flowing through it. Show a torch bulb cannot be used to detect with electric current flowing through a liquid in a circuit. 27. How do we detect electric current flowing through liquids? Answer: the with electric current flowing through liquids having low electrical conductivity can be detected in two ways: i) by using a LED ii) by using a compass. 28. Write the full form of "LED". Answer: light emitting diode. 29. Ho