Nothing is visible to our naked eyes when we enter a fully black room, yet everything becomes visible the instant we turn on the light. This is due to the fact that light may be sensed by the human eye. It allows us to see what is going on around us. We can't see anything if there's no light.

Light sources

Definition of luminous objects: Luminous objects are defined as objects that can produce light by themselves.

Sun, torchlight, fireflies, candles, jellyfish, and many more are examples.

The sun is the primary source of natural light. During the day, light from the Sun falls on objects (such as trees, chairs, and homes) and allows us to see what is around us. Sunlight is essential to the photosynthesis process of plants. All living creatures on the planet rely on the sun’s light in some or other way.

Definition of non-luminous objects

Non-luminous objects are objects that do not produce light within their own body.

Wood, book, box, paper, and other materials are examples.

Types of objects based on how they interact with light.

Objects may be categorized into three groups based on how light interacts with materials. Depending on how much light travels through it, an item may be transparent, translucent, or impenetrable.

Transparent objects

Transparent objects are those that enable light to flow entirely through them.

Clear drinking water, glasses, and rivers and lakes are some examples.

Translucent objects

Translucent objects are those that allow light to flow through them partly.

A rough window glass, buttered paper, wax, and other materials are examples.

Opaque objects

Opaque objects are those that do not allow any light to flow through them.

Examples include a brick, a wall, cardboard, stone, and so forth.

Definition of Shadow.

Light moves in a straight path but will not pass through an opaque object. When light is hindered by an object, a dark region known as a shadow forms on the backstopicIde of the object.

Shadows are always created on the other stopicIde of a light source. To cast a shadow, a light source and an opaque object are required. 

Shadows are only seen on screen-like surfaces like the wall of a room, a structure, the ground, and so on.

An object's shadow is always black, regardless of its color, and it may not provtopicIde information about the shape of the object.

Pinhole camera

The pinhole camera operates on the premise that light travels in a straight path. When compared to the actual object, you would observe that a small inverted image is generated.

Uses of pinhole maera 

A pinhole camera may even be used to see an eclipse. You can view a distant object through the opening of the smaller box under bright light.

When a candle is kept near the pinhole camera at a decent distance, you may see an inverted image instopicIde the pinhole camera screen.

Proof light travels in a straight line

When a lit candle is placed at one end of the table, it can be seen through a rubber pipe standing at the other end. However, since light travels in a straight path, you cannot see the lit candle when the rubber pipe is bent. This proves light travels in a straight path.