Skip to main content

CBSE Class 3 Science: Light, Sound and Force

  • We need light to see the objects around us.

  • Sun is the ultimate source of light on Earth.

  • We also get light from objects like bulb, torch, candle, lantern, oil lamp and table lamp.

  • Luminous Objects: Objects that give light.

  • Non-luminous Objects: Objects like table, chair etc that do not give light.

  • Transparent Materials: Materials like glass, air etc that allow light to completely pass through them.

  • Translucent Materials: Materials like frosted glass and butter paper that allow light to pass through them partially.

  • Opaque Objects: Objects like wood, bricks etc that do not allow light to pass through them.

  • Rays: The straight lines along which light travels.

  • Shadow: A shadow is formed when an opaque object blocks the path of light.

  • Our Earth moves around the Sun. And the moon revolves around the Earth.

  • Earth and moon do not have light of their own. They receive light from the Sun and reflect the light that falls on them.

  • Solar Eclipse: On some new moon days the moon comes in between the Sun and the Earth and blocks the sunlight from falling on Earth. A shadow of the moon is formed on the Earth and people in this shadow region cannot see the Sun either totally or partially, for sometime. Such a phenomenon is called a Solar Eclipse.

  • Lunar Eclipse: On some full moon days the Earth comes in between the Sun an the Moon and blocks the sunlight from falling on the Moon. A shadow of Earth is formed on the Moon and thus people cannot see moon (partially or totally) for sometime. Such a phenomenon is called a Lunar Eclipse.

  • Sound: We hear different sounds around us. We produce sound when we speak or laugh.

  • Pleasant Sounds: Soft sounds that make us happy.

  • Noise: Unpleasant sounds that irritate us and make us sick. Unpleasant sounds cause noise pollution.

  • We should avoid noise pollution by speaking softly, playing music / TV in low volumes etc.

  • We do different types of works in our daily life. For doing work we either push or pull something by applying force on it.

  • What is force? The push or pull applied on an object is called force.

  • Effects of force:
    1. It can move objects.

    2. It can stop moving objects.

    3. It can change the shape of an object.

    4. It can change the direction of a moving object.


Popular posts from this blog

Seemantham - The South Indian Traditional Baby Shower ceremony

Seemantham is a traditional south Indian way of celebrating baby shower. The same is celebrated in north India as 'godbharai' ('god' means lap in Hindi - 'd' in 'god' is pronounced as 'the' and bharai means 'to fill'). The celebration differs from region to region. Seemantham is also known by the names 'poolu mudupu' (i.e adoring flowers in the hair) and 'gajulu todagadam' (i.e wearing glass bangles) in Telugu. It is celebrated in the 5th or 7th or 9th month of pregnancy. Seemantham is one of the 16 Hindu samskaras known as 'simantonnayana' in Sanskrit. It is a samskara of the embryo / foetus that develops in the pregnant woman's womb. Usually, seemantham is celebrated for the 1st pregnancy only and not for the subsequent conceives. There are certain superstitious believes on celebrating the function. In the olden days, people believed that pregnant women are easily prone to 'dishti' or evil e

How To Perform Aksharabhyasam At Home And Basar temple

Aksharabhyasam Meaning The word 'Akshara' means letters (alphabets) in Sanskrit and 'abhyasam' means practice. Aksharabhyasam is a traditional religious function of Hindus. It is also known as 'Vidyaarambham' which literally means starting of education. In this function a child is given initiation for writing / education. With this function the child is ready to receive formal education in a school. The function is performed in different ways in different regions of India. When to perform aksharabhyasam In the olden days, aksharabhyasam was performed when the child was 5 years old. But presently because of early education at Kindergarten level, parents perform this ceremony when the child is in his 3rd year i.e. after the child completes 2 years. Normally there is a belief that aksharabhyasam should not be performed after the child completes 3 years and is in its 4th year. Where to perform aksharabhyasam The function can be performed either in a temp

School Speeches - Farewell Speech By School Principal to Outgoing Students

Author Reserves All Rights. Listen to the speech in my YouTube Channel: This sample speech would be helpful for the school principal to deliver on the occasion of school farewell day party. Respected teachers and my dear students, Good Morning / Good Afternoon to each one present here and a very warm welcome to you to the school farewell party. It's a nostalgic feeling as I remember my student life in school and my school farewell party. I am sure we all have mixed feelings on this day which is a blend of joy and sadness. On one hand you feel enthusiastic as you will be stepping into a completely new different world where you will find relatively more freedom than in a school life. While on the other hand you will feel sad as you have to depart from your school / classmates. My dear friends the time has come to bid you all farewell with a heavy heart from this esteemed institution which protected you, cared for you, supported you and guided you all these years.