Science Class 3 Chapter 9 Full Details

Science Class 3 Chapter 9 Full Details

Science Olympiad in grades 1-12, like a basketball or hockey team, involves year-round training, dedication, guidance, and practice. The National Science Olympiad (NSO) test is a global Olympiad competition in which students from all over the globe participate. It gives a platform for emerging talent to showcase their skills. Learners require these tests to prepare both for national and international competitions. This page is about Science Class 3 Chapter 9.

Science Olympiad Questions Class 3

Science Class 3 Chapter 9: Light, Sound, and Force

Shadow and Light

Light is a sort of energy that is vital to our everyday life. Plants cannot grow in the absence of light because they require sunshine to make their food, and animals and people would go hungry if plants did not exist.
We see with our eyes, yet we can’t see anything if there’s no light. We’ve found that in full darkness, no item is visible.

Characteristics of light

  • Light travels in a straight line at all times.
  • Light travels in a straight line in the form of rays. It has a maximum speed of 300,000 kilometers per second! The only way to bend light is to stop it. Until it collides with something else, light will continue to move in a straight path.
  • As indicated by shadow casting, light travels in a straight path.
  • Light reflects as it touches a surface.


A shadow is created when light cannot travel through an opaque object. When an opaque item stops the path of light, the light that falls on it is unable to reach the opposite side, resulting in darkness in that area.

The rest of the space is lighted since there is nothing to block the light from going through.
The item must be opaque or translucent in order to cast a shadow. Obscure items cast dark shadows, whereas translucent objects cast weak shadows. Because all light goes through a transparent item, it does not cast a shadow.


When anything vibrates, waves of energy (vibration) are sent into our ears, resulting in sound. Vibrations are transmitted to the ear via air or another media (solid, liquid, or gas). The vibrations are stronger when the sound is louder. As you go away from the source, the sounds get fainter.
The sound is affected by the pace at which an item vibrates to create sound waves. The pace of vibrations determines the pitch of a sound (high or low).

Different materials produce different pitches; we hear a high-pitched sound when an object vibrates fast, and we hear a low-pitched sound when an object vibrates slowly. The majority of sounds are made up of a variety of sound waves.


We utilize our muscles to pull and push objects in our daily lives: we draw a glass of milk to our lips, we push an object to move in a specified direction, and so on. We understand that moving an object needs a “pull” or a “push.” A push or pull on an item is defined as force.

Walking, lifting items, throwing objects, moving objects from their initial place, and so on all require force. In a nutshell, force is present in every aspect of our lives. When we want to move or stop anything, we normally utilize force, although this isn’t always the case. A wall does not move when we exert force on it.

Motion is halted by force

An object stops moving when we apply more force in the opposite direction of the motion.

For example, if we try to hold the ball thrown to us with a force greater than the force with which it is being thrown, it will stop.

As a result, we can say that force can also be used to stop a moving object.

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