The Scando Review
The Scando Review
Light, the source of everything we see

Light, the source of everything we see

Today we live in a world with many facilities available at just a click away. Can you imagine a world without light and electricity now? We now wonder how it was possible for humans to live without light!

Sunlight is the most easily accessible source of available light for us. The earliest form of artificial light was fire. In ancient times, the first step towards the development of civilization is said to be the discovery of fire. Early humans made fire by rubbing two flint stones, and then later by burning wood, oil, candles, etc. Today we produce light mostly by using electricity.

Apart from sunlight and visible electrical lights, no single answer to the question ‘what is light’ satisfies the many contexts in which light is experienced by human beings.  Light may be called an electromagnetic radiation that can be detected by the human eye. Apart from giving the sense of sight, light from the Sun warms the Earth, initiates the life-sustaining process called photosynthesis in plants, and drives global weather patterns, etc. On the grandest scale, light’s interactions with matter have helped shape the structure of the universe. Light acts as a window to the universe. Almost all information about the rest of the universe reaches the Earth in the form of electromagnetic radiation.

Light is vital to all forms of life. Light significantly supports body functions. Light can affect our mood, productivity, improve sleep patterns, help memory consolidation and has a myriad of other functions too. Basically, the effects of light depend on its intensity, timing, duration, wavelength, and so on.

Light influences the sleep-wake cycle, promoting alertness during the day and having a beneficial effect on our performance and mood.

How light is reflected was a question that plagued the minds of scientists when they started to study light. According to Britannica, Pythagoras (about 570 BC– 490 BC) proposed that sight is caused by visual rays coming from the eye and then striking objects. Empedocles (about 490 BC – 430 BC) seems to have developed a model of vision in which light was emitted by objects and the eye. Epicurus (about 340 BC – 270 BC) believed that vision is produced when light reflects off objects and enters our eye. Euclid (about 325 BC – 265 BC) presented a law of reflection.

Electromagnetic radiation

Light is a sort of electromagnetic radiation, which occurs within an extremely wide range of wavelengths from gamma rays to radio waves, which are measured in metres. According to the NASA Science website, within the broad spectrum, the wavelengths visible to humans occupy a very narrow band – from about 400 nanometres to 700 nanometres. The spectral regions adjacent to the visible band are often referred to as light, with infrared at the one end and ultraviolet at the other.

Body clock

While we talk about light and its effects, one of the bigger effects most of us are not aware of is the biological effects. Light helps set a biological clock in our body; it has the ability to act as a timekeeper of our body clock.

Getting exposed to natural light is very important for our wellbeing – it supports a healthy circadian rhythm that affects our physical, mental and behavioural changes.

Light influences the sleep-wake cycle, promoting alertness during the day and having a beneficial effect on our performance and mood. This happens because of the presence of light-sensitive receptors in the eye’s retina. The retinal ganglion cells suppress the secretion of the sleep hormone, melatonin from the pineal gland. During the evening and at night, the melatonin level rises and promotes and prepares the body for rest and sleep.

Circadian rhythm

A majority of us spend time indoors. Getting exposed to natural light is very important for our wellbeing – it supports a healthy circadian rhythm that affects our physical, mental and behavioural changes. These natural processes affect most living things, including animals, plants and microbes. Chronic disruption of sleep and circadian rhythm is associated with long-term and short-term health issues. Sleep patterns are directly connected with our circadian rhythm, and light can correct the circadian rhythm.

Our mood is related to light exposure, too. Light, which stimulates the circadian system, has a direct mood enhancing effect. Being locked in a dark room for many days, even for one day, can turn off our good mood. Light has the ability to lessen stress. According to, Swedish researchers have proved the importance of adequate lighting in the school ambience. Adequate lighting will reduce stress among schoolchildren. Also, light therapy has been used as a part of treatment for depression for many years.

Harmful effects

If light radiation exceeds a certain level, it will be harmful for us. Excess luminous intensity will affect mainly the eyes. This is particularly because the energy absorbed from the light is converted into chemical energy, which might result in the formation of reactive forms of oxygen that attack cellular structures and even DNA. This is why it is not recommended to look into a bright source of radiation from a short distance for long. Lasting damage to the retina could be caused by looking at the Sun or powerful sources of artificial light without any eye protection gear.

Light affects us day and night. Too much exposure to light in late evenings may lead to sleep delay and difficulty in falling asleep. Our late-night screen time does not allow our body to rest and sleep properly. Increased use of laptops, computers or mobile phones at night might cause sleep delay and thus will have a negative impact on our circadian rhythm.

Light, is the beginning of everything we see and is one of the most important parts of our life. Be the light to your children.

Now put on your thinking hats and think about the following questions for a couple of minutes.

How would you describe the term “electromagnetic radiation” to your students?

Can you think of the harmful effects that can be caused if the light radiation exceeds a certain level?

Write down your thoughts and discuss them with your students, children and your colleagues. Listen to their views and compare them with your own. As you listen to others, note how similar or different your views are to others’.

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Happy Teaching!