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Light Energy

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Last updated date: 29th Mar 2024
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Light Energy - Uses and Properties of Light Energy


This article has been prepared by the subject experts at Vedantu, discussing important concepts related to light energy. This will help students get conceptual clarity about the topic and will help them solve any question related to the topic. 


Download the free PDF notes of the topic from the website or mobile app of Vedantu or watch the video lecture to understand the topic well.


Table of Content:

  • What is Light?

  • What is Light Energy?

  • Type of Light Energy

  • Properties of Light Energy

  • Use of Light

  • Use of Light Energy

  • Use of Light in Physics 

  • Key points from the Chapter

  • Frequently asked questions


What is Light?

Light is a form of energy. Light plays a very important role in our lives because without it we would have to survive in the dark walking endlessly without any start or an exit. 


We know that the sun is the natural source of light; however, there are other sources that also emit light such as electric bulbs, candles, torches, kerosene lamps, and so on.

We know that the speed of light is 3 x 108 m/s and nothing can travel faster than this speed. However, according to the theory of relativity, objects can travel faster than this speed.


What is Light Energy?

The energy produced by vibrations of electrically charged particles is light energy. The examples of light energy are:

  • The energy that we use to cook food in a microwave oven is a form of light energy.

  • Army men use radar to get the searchlight beam on the target.

  • Radar systems that are used for ATC (air traffic control) use a form of light energy.


What are the types of Light Energy? 

Following are types of Light Energy - 

  • Visible Light - They are the form of electromagnetic energy and can be seen only through naked eyes. Naturally, the Sun is the source of Visible light, Whereas, flashlights, bulbs are some of the man-made sources.

  • Infrared Light - They are a form of electromagnetic energy which produces heat. Tv remotes, AC remotes are the most commonly used Infrared light. 

  • X-rays and Ultraviolet Light - They are lights with short wavelengths. Used by doctors to monitor the inside of a human body.


 Properties of Light Energy 

  • Intensity - The rate at which light emits from the source per unit area is the intensity of light, which is measured in Watts.

  • Frequency - the number of waves that can pass via a point in space during the time interval.

  • Wavelength - It is the distance between the two consecutive crests or troughs of a wave.

  • Polarization - when all the waves vibrate in a single plane, then we can say that the light is polarized.

  • Phase - A point in the time period during the cyclic


Uses of Light Energy

  • Food formation

  • Growth of the human body

  • Regulation of Physiology

  • Sight and vision

  • Heat and temperature

  • Drying & evaporation

  • For speed regulation

  • Source of electrical energy

  • Chemical analysis by spectroscopy

  • Sanitation of earth

  • Killing germs viz: microorganisms

  • Signaling system

  • Sterilization process

Now, let’s discuss these in detail:

 

Uses of Light

Food formation

  • The food we obtain from plants is only possible because of light. A light helps plants in undergoing photosynthesis. The light obtained by the plants is used in preparing food for itself and for human beings.

  • We know that Vitamin D is beneficial for us. So, for gaining this energy for free, Sun is the best provider of this nutrient. 

  • The light energy we get from the sun can be utilized for domestic purposes like we can use these for operating solar cookers. We also find the use of sunlight for solar water heaters.

  • Light is the only source that helps us see beautiful things around us.


Light maintains our body clock

As we can see, we remain active all day and relaxed at night. Similarly, sunflowers rejoice by spreading their leaves and they always face towards the sunlight; however, they fade after the sunrise.

 

In Physics

  • Visible light in the electromagnetic radiation in the range of an electromagnetic spectrum that is perceived by the human eye.

  • A human eye can distinguish between 6,000 shades of a particular color, all this is possible because of the light. Light has various electromagnetic spectrum, where each spectrum has seven following colors (VIBGYOR):

  1. Violet

  2. Indigo

  3. Blue

  4. Green

  5. Yellow

  6. Orange 

  7. Red


Each of these colors has a unique wavelength and frequency. And when light falls on an object, it absorbs light of some wavelengths and reflects others. 

So, when the light falls on any object, it absorbs some spectra of light and reflects the remaining and whichever color it reflects, becomes the visible color. However, the colors that are absorbed are not visible to us, only the color it reflects is visible to us.

 

In Spectroscopy

We use spectroscopy for both quantitative and qualitative analysis of various compounds; however, all this is possible because of light. Spectroscopy also has many forms and these vary with the wavelength of light used in each.

 

For Sterilization

The ultraviolet component of light is an excellent sterilizing agent. You might’ve noticed the use of UV lamps in supermarkets and hospitals; these UV lamps are the best sterilizers.

 

The UV rays kill the microbes in the air keeping the area of the supermart or hospital sterile. That’s why UV light is considered a dry method of sterilization.

 

Sunlight is one of the effective sterilizing agents that helps kill all the microbes present in the blankets or other mattresses of hospitals.

 

Light as a Source of Drying and Evaporation

Sunlight helps in the drying of wet clothes, the soil, forests, air, and rocky surfaces due to their ability to heat up. Light also helps water evaporate from oceans and ponds. This drying is helpful in the following two ways to live on earth:

 

1. Water Cycle:

The water cycle is a way by which freshwater on the earth’s surface keeps recycling for drinking and irrigation purposes. The water from the surface evaporates to form clouds.

 

These clouds burst in the form of raindrops to return the freshwater to the surface of the earth. So because of the rain, we get fresh water to drink and also use it for irrigation.

Without the water cycle, all the water on the earth would have remained in the ocean we would have no water to drink.

 

2. Scavenging:

Sunlight keeps our nature clean. Sunlight prevents the growth of weeds, algae, and other microbes keeping the environment clean and tidy. 

 

Because of the sunlight, the dead bodies and other waste material get dried and lose their mass, and degrade  (reduced in quantity) fast.

 

Key Points from the Chapter:

  • Light is a form of energy

  • There are two types of sources: natural and manmade, Sun is the natural source whereas, bulbs, candles, lights are the man-made sources.

  • The speed of light is the fastest 

  • Light and Energy has various uses and applications

  • Without light, the process of  food formation and the very existence of life on the Earth will be impossible


FAQs on Light Energy

1. List the Forms of Light Energy?

The forms of energy are classified below:

  • UV light

  • X-rays

  • Visible light

  • Infrared light

2. List the Properties of Light Energy?

  • Intensity - The rate at which light emits from the source per unit area is the intensity of light, which is measured in Watts.

  • Frequency - the number of waves that can pass via a point in space during the time interval.

  • Wavelength - It is the distance between the two consecutive crests or troughs of a wave.

  • Polarization - when all the waves vibrate in a single plane, then we can say that the light is polarized.

  • Phase - A point in the time period during the cyclic waveform.

3. How Does Light Produce Energy?

Light is a form of chunks or packets called photons, where each photon is an    integer. 

Photons continue to emit from the light bulb. Since the persistence of vision is 1/16s, so we cannot observe the quick fluctuation or the release of photons from the bulb.

4. Is Light Energy Kinetic Energy?

Yes. Light energy is kinetic energy. It travels in the form of waves with a speed of 3 x 108 m/s

5. What is the significance of light energy?

Light energy has uncountable functions and significance. Sun provides the light which is used by plants for photosynthesis thus making the food available for all organisms.  Visible lights make us see objects around us. Light energy affects the temperature of the water, affects the relationship between predators and prey. 

Thus, light controls the growth and development of the whole ecosystem.

6. Can light be controlled in natural conditions?

The flow of light is not always equivalent. In a natural ecosystem, various factors affect the inflow of light. For example, topography affects the insolation of light. Ice has high albedo i.e - more light is reflected back by the white snow. On the other hand, hard and dark topography attracts more light examples, black soil. Similarly, other factors vegetation, cloudiness, seasonal patterns, and variation of day and night affect the inflow of light on the Earth.  The factors are discussed in detail in the article and the video lectures.

7. What is the artificial form of light energy?

Apart from the Sun which is the natural source of light energy, other forms of artificial light energy are lights generated through bulbs, lanterns, LEDs to emit light when it is naturally dark. India mainly is dependent on fossil fuels to generate artificial light, however, this form of light energy pollutes and disturbs the natural ecosystem. And, thus we focus on preserving and utilizing the natural source of light.

8. Is the topic Light Energy difficult to understand?

The topic in itself is not very difficult yet many students get confused while trying to understand the topic. Thus for a better understanding and concept clarity, the experts at Vedantu have compiled the information related to the topic in the most lucid language. The systematic organization of the topic helps the students grasp the concept very easily. Students can also watch the video lecture related to the topic or can connect with the faculty through the helpline number in order to clarify any doubts related to the topic.

9. What are the challenges caused by artificial light energy?

Artificial light energy is the form of light energy generated by human beings. Fossil fuels are the main source of generation of these light energies. It has the following harmful effects- 

  • Light pollution disturbs the natural ecosystem, causing the decline of biodiversity

  • Causes air pollution by emissions of harmful greenhouse gasses in the process of light generation

  • The larger impact of global warming and climate change 

Because of these harmful effects, India mainly focuses on promoting the use of the natural source of light energy. Therefore, promotion of the National Solar Mission.