Light |Brightness of Light | Sources of light |Mirrors | Transmission of light | Reflection of light.

Light: In today's blog you will learn about the light, 'Reflection of light'. This is a very important topic according to your pre-matrix exams, matrix exam and the civil services exam. So let's start it. 

Light

Reflection of light: “Mirror not only reflects our image but also our behaviour.” Anyone guesses that on which topic our today's article is. If you think ‘light' you are right. So, first, answer this question ‘ Why things are not visible in the darkroom?’ anyone guesses. Ok. So when we are in a dark room there is no light. That means no vision. But when we turn on light we are able to see because light rays reflect and reach our eyes. Now without wasting time let’s start the lesson.

Light is a form of energy

Light

Light itself is a form of energy that travels as tiny elements of electromagnetic energy called photons. When photons enter our eyes, they incite special light-sensitive cells so that we can see. Other forms of energy that travel as electromagnetic waves include radio waves, x-rays, and microwaves in microwave ovens. Light is a type of electromagnetic radiation(wave) that carries energy.

What is ‘LIGHT’? 

Light is electromagnetic radiation which makes sense of vision. Light can move as wave(electromagnetic radiation) or particles(photons).

What makes things visible?

During the day,  the sunlight enables us to see objects.  An object reflects light that drops on it. This reflected light,  when acquired by our eyes,  facilitates us to see things. We are able to see through a  transparent channel as light is transmitted through it.  There are a number of ordinary wonderful phenomena correlated with light such as image formation by mirrors,  the twinkling of stars,  the beautiful colours of a  rainbow,  bending of light by a  medium and so on.

Brightness of light 

The farther you are from a light, the less bright it will seem. This is because light spreads out in all directions from its source. So when you are far away, the light is spread over a wide area. Many stars, for instance, are much brighter than our Sun, but their light is spread out over so vast an area that by the time it reaches us, the stars do not even seem as bright as a candle.

Sources of LIGHT  

Sources of light

Things that emit light are called light sources. Many different objects give off light. The Sun, stars, fire and lightning are some of the natural sources of light. Even some animals like jellyfish, fireflies and some types of mushrooms can create their own light, this is called as bioluminescent. Light created by humans is artificial light. Flashlights, table lamps, electric light bulbs, and fireworks are some of the artificial sources of light.
The Sun shines because it generates energy wide in its core. The energy is made when atoms unite together in nuclear fusion reactions. The Sun flames off the energy into space in all directions in the form of electromagnetic radiation. Some of the radiation visits to Earth as the light and heat we know as sunlight. The Sun is a luminous light origin because it creates energy inside itself.
Some sea organisms can make their own light. This capacity is called bioluminescence, which means giving rise to light biologically. Some bioluminescent sea creatures include shrimp, squid, and starfish.

Light and shadow 

Light and Shadow

Light travels in straight lines, so, in most cases, it cannot go around obstacles in its path. When light rays hit a solid object, some bounce back and some are absorbed by the object, warming it up a little. The area behind receives no light rays and is left in shadow. Shadows are made by blocking light. In short, Light rays travel from a source in straight lines. If an opaque object gets in the way, it tops some of the light rays from travelling through it, and an area of darkness appears behind the object. The dark area is called a shadow. The size and pattern of a shadow depend on the stance and quantity of the light source compared to the matter.

Umbra and Penumbra

Shadows are not totally black. If you stare nearly at a shadow, you will see a dark region in the centre and a lighter area around it. The main dark area, called the umbra, occurs where rays of light from the source are entirely obstructed. The outward area, called the penumbra, is lighter because some rays do get through.

What is meant by ‘Reflection of Light’? 

When light rays fall on an object their direction changes and they turn back. This is called the reflection of light. Due to the reflection, we are able to see the objects around us.
What are the ‘Laws of Reflection of Light’?
Laws of reflection are as follows:
(i) The angle of incidence is proportional to the angle of reflection.
(ii) The incident ray,  the normal to the mirror and the reflected ray,  all lie in the same plane.
(iii) The incident ray and the reflected ray are on opposite sides of the normal.

Reflection of light 

These laws of reflection are relevant to all kinds of reflecting surfaces including spherical surfaces.

Incidence ray

The beam of light that falls on an object is an incidence ray. The point at which the incidence ray falls is the point of incidence.

Reflected ray 

The rays going away from the surface after reflection are called as the reflected rays.

Normal 

The point on the reflecting surface on which incidence ray falls and from which reflected ray reflects is the Normal of the reflecting surface.

What are the different ‘Types of Reflection’?

 Following are the main two types of reflection.
(i) Regular reflection of light: The reflection of light from a plane and smooth surface is called a regular reflection of light. For regular reflection, the angles of incidence as well as of the angle of reflection are the same for all parallel rays falling on the surface. Thus the reflected ray are also parallel to one another.
(ii) Irregular reflection of light: Reflection of light from a rough surface is called an irregular reflection of light. In irregular reflection, the angle of incidence for parallel rays of incidence are bot equal and therefore their angles of reflection are also not equal. Thus, the reflected ray is not parallel to one another and spread over a large surface.

Types of reflection of Light

Laws of reflection are followed in both regular and irregular reflection. The reflection of light in irregular reflection has not been obtained because the laws of reflection are not followed. They are obtained because the surface is rough(irregular). In irregular reflection the angle of incidence at different points are different. But at any one point, the angle of incidence and reflection are equal.

 Light speed 

Light waves and all other electromagnetic waves travel at 1,86,000 miles  (300,000 km) per second, which is so fast that they could circle the world almost eight times in a second. Nothing in the cosmos can travel faster than light. The velocity of light in vacuum commonly as c, is a universal physical constant important in many areas of physics. Its exact value is 29299792458.

Light year 

A light-year is an expanse travelled by light in one year. As the speed of light is approximately 3,00,000 km/s, the light-year is equal to 9.5 × 10^12 km. Light takes 1 second to reach the earth while it takes 8 minutes to reach us from the Sun. So now you can think that ho Structure of periscope w fast light is.

 Periscope

Structure  of periscope 

A periscope is an instrument made by using the principles of reflection of light. It is used for observing over and around it. It was foremost used in World War I. It’s made by fixing the mirrors or prisms at a perfect angle of 45° at both as you can see in the following image.

Uses of Periscope 

Periscopes were first used in the  World War I. In world war I periscope rifles were used. Periscope binoculars were used in the world war I by the troops. Periscope is also used in the armoured vehicles like tanks. It helps the to inspect the condition through the vehicle roof. Periscope sights were introduced during world war I. But nowadays periscope has very important Naval use. It’s mainly used in submarines to see objects above and keep a watch on the objects above the surface of the water. It is also used to observe and keep a watch on the objects or persons on the ground from an underground bunker.
Our this lesson is completed but part 2 is remaining. Part of this lesson will be available earlier.