Tuesday, 7 January 2025

LIGHT SHADOW AND REFLECTION CBSE CLASS 6

 

DR OMAR CLASSES BARRA – 3, KANPUR NAGAR

Light as a form of energy

  • Light is the energy that enables us to see.
  • Light is emitted from a source such as the Sun.

To know more about Light Energy, visit the link below;

Is Light a Traveler?

Rectilinear Propagation of Light

Light takes the quickest path between any two points. Therefore, light travels in a straight line. This is known as a rectilinear propagation of light.



Transparent, Opaque and Translucent Objects

Luminous and Non-luminous Objects

  • Objects that emit light and heat are known as luminous objects. For example, Sun and other stars
  • Objects that do not produce their own light but reflect the light emitted by luminous objects are known as non-luminous objects. For example, the Earth and the trees

Transparent, Opaque and Translucent Objects

Objects can be classified based on their interaction with light.

  • Transparent objects allow light to pass through them without getting scattered. For example, glass
  • Translucent objects allow light to pass through them partially. For example, Butter paper
  • Opaque objects do not allow any light to pass through them. For example, a table, a book, etc

What are Shadows?

Shadow Formation

  • A shadow is formed when an opaque object comes in the path of light.
  • A shadow needs a screen where it is formed, for example, the ground, walls of a room or even the surfaces of buildings.
  • Shadows give us an idea about the shapes of different objects. Also, it can even mislead us about the shape of different objects. E.g. the shadow of a cone appears to be a triangle on the screen.



The Pinhole Camera

Formation of Image by Pinhole Camera

  • A pinhole camera is a simple camera that consists of a light-proof box, a thin film for a screen and a small aperture or hole to allow the passage of light rays.
  • The light from outside enters through the small hole and forms an image on the screen that is inverted.



Mirrors and Reflection

Mirrors

A mirror is a surface usually consisting of glass that reflects light incident on it to form clear erect images.

Reflection

When light is incident on a surface, it gets reflected or bounces back. Any surface that is really well-polished or shiny acts like a mirror. The phenomenon of light bouncing off surfaces is called reflection.

Characteristics of Images

  • Images have colour, unlike shadows. They are formed due to the converging rays of light that come after reflecting from objects.
  • A real image is formed by the actual convergence of light rays. Real images always form on a screen.
  • A virtual image is the apparent convergence of diverging light rays. Virtual images cannot be obtained on a screen.

Plane Mirrors and Images Formed by Them

A plane mirror changes the direction of light that falls on it.



This enables us to see images. Take the example of a comb placed in front of a mirror over a dark-coloured paper. Let a beam of light pass through the comb on the mirror using a torch. Then an image is observed similar to the one given :



We observe that the light gets reflected from this mirror, and it travels in straight lines.

Q1What is the definition of light?

The energy derived from the sun, a lamp, etc., that allows you to see things is called light.

Q2 What is a range of visibility?

The horizontal distance (in kilometres or miles) at which a large dark object can just be seen against the horizon sky in daylight.

Q3 What are the uses of spherical mirrors?

1. Used as a rear mirror 2. Security mirrors 3. Surveillance mirror

 

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