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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...
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Class 10 Science Notes- Chapter: Life Processes

 TOPICS TO BE COVERED IN THIS MODULE

  1. Life Proceeses
  2. Nutrition
  3. Respiration
  4. Transportation
  5. Excretion

Life processes:

Life processes are the essential functions that living organisms perform to maintain their life and ensure their survival and continuity on Earth.

Examples:
  • Nutrition
  • Respiration
  • Transportation
  • Excretion

Nutrition:

The process by which living organisms obtains and utilises its food is called nutrition.

Role of food: 

  1. To produce energy
  2. Build new cells for growth and development
  3. Repairing of cells

Types of nutrition:

1) Autotrophic Nutrition:

  • The mode of nutrition in which organisms prepare their own food is called autotrophic nutrition.
  • The organisms which show autotrophic nutrition are called autotrophs.
  • Examples includes green plants, blue green algae.

2) Heterotrophic Nutrition:

  • The mode of nutrition in which organisms depend on other organisms for their food is called heterotrophic nutrition.
  • The organisms which show heterotrophic nutrition are called heterotrophs.
  • Examples include human beings, animals etc.
Now lets discuss Autotrophic nutrition in more detail:

Autotrophic nutrition is further divided into two categories. They are:
  • Photosynthetic Autotrophic Nutrition
  • Chemosynthetic Autotrophic Nutrition
Photosynthetic Autotrophic Nutrition: The mode of nutrition in which organisms use light energy to synthesize their own food from inorganic substances like water and carbon - dioxide. Examples are green plants, blue green algae.

Chemosynthetic Autotrophic Nutrition: The mode of nutrition in which organisms utilize chemical energy to synthesize their own food from inorganic substances like NH3, NO2. Examples are Purple- sulfur bacteria.

Autotrophic nutrition includes:
  • Carbon dioxide which plants get from air.
  • Water which they get from soil.
  • Light is from Sunlight
  • Chlorophyll is from Chloroplast.
Photosynthetic Reaction:


During photosynthesis, green plants take in carbon dioxide from the air and water from the soil. Using sunlight and chlorophyll (the green pigment in leaves), they convert these raw materials into glucose (a type of sugar) and release oxygen as a by-product, also lose some water through stomatal pores.











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