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Sound – Class 9 Science Complete Notes

1. What is Sound? Sound is a form of energy which produces a sensation of hearing in our ears. Sound is produced by vibrating objects. Examples include vibrating tuning fork, vocal cords in humans, bells, musical instruments, etc. Vibration: Rapid to-and-fro (back and forth) motion of an object. Short Question: Can sound be produced without vibration? Answer: No, sound cannot be produced without vibration. 2. Medium of Sound The substance through which sound travels is called a medium . Sound can travel through solids, liquids, and gases but cannot travel through vacuum . Process of Sound Propagation: When an object vibrates, it makes the air particles around it vibrate. These air particles move back and forth from their original (rest) position. The vibrating air particles push nearby air particles. This causes the nearby particles to also start vibrating. In this way, vibrations pass from one particle to another. This process continues through the medi...

CLASS 9 SCIENCE NOTES: CHAPTER - TISSUES

What Are Tissues? Group of cells with a common origin and similar function are called tissues. Multicellular organisms have specialized cells forming tissues. Utility: Provide structure, mechanical strength, and division of labor. Types of Tissues Plant Tissues Animal Tissues Plant Tissues 1. Meristematic Tissues Cells actively divide for growth. Intercellular spaces are absent. Shapes: spherical, oval, polygonal, or rectangular. Have thin walls, few/no vacuoles, dense cytoplasm, prominent nuclei. Type Location Function Apical Tips of stems/roots Increase length (primary growth) Intercalary Base of leaves/internodes Longitudinal growth Lateral Sides of stems/roots Increase thickness (secondary growth) 2. Permanent Tissues Cells loose ability to divide, differentiate to...

CLASS 10 SCIENCE NOTES: CHAPTER- LIGHT: REFLECTION AND REFRACTION

Topics covered:   What is light?  Laws of Reflection Plane & Spherical Mirrors Refraction Lenses What is Light? Light is a form of energy that enables us to see objects around us. Its speed depends on the medium through which it travels. The speed of light in vacuum is 3 × 10 8 m/s . Light always travel in a straight line and this principle is known as Rectilinear propagation. A bundle of light rays forms a beam of light . Reflection of Light The phenomenon of bouncing back of light from a polished surface (like a mirror) is called reflection . Points to remember Incident ray: Incoming ray that strikes the surface. Reflected ray: Ray that bounces back after striking. Normal: Imaginary line perpendicular to the surface at the point of incidence. Laws of Reflection The angle of incidence (i) is equal to the angle of reflection (r): i = r . The incident ray, normal and ...

CLASS 10 SCIENCE NOTES: CHAPTER - CONTROL AND COORDINATION

Coordination means working together of the various organs of an organism to adjust various activities of life. Control & coordination ensures: Correct movement for each specific change (stimulus). No wrong or unnecessary actions. Stimulus (Stimuli): Any change in the environment (internal or external) that produces a response in an organism. Example: Light, sound, smell, touch, temperature. Receptors:  R eceptors are specialized structures that can convert various types of energy (stimuli) into the electrical signals (nerve impulses) used by the nervous system Nervous System:  The nervous system is composed of specialized tissues, called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. Functions of the nervous system: To receives information from the environment through sense organs. To act according to through muscles and glands. A neuron is the structural and functional unit of the nervous system. Synapse:  The gap between the ...