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
