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Light Facts

Optics is the study of the properties of light and how light behaves: how light is produced, how light can do work and how light can be converted into another form of energy, how light travels, why we see, etc.

Light is the only form of energy that we can actually see with our naked eyes.

Sometimes light can be formed by chemicals reacting with one another, or radiation, or other mechanical means, such as when fire is produced, when a candle is lit, or when a battery is connected to a light bulb.

Sir Isaac Newton saw a rainbow of colors when sunlight went through a glass prism. He also noticed that the light was bent and separated when it was directed through a prism.

The colors he saw were red, orange, yellow, green, blue, indigo, and violet. This is called the light spectrum.

isaac-newton-facts

Newton called the color between blue and violet ‘indigo’ so that he could list seven colors.

He considered ‘seven’ as being the perfect number that is built into all the laws of nature. At the time, he had no idea about ultraviolet because this color cannot be seen with the naked eye.

The reason we see colors is that each color band has a different wave length and travels through the prism at different speeds.

light-spectrum

The same thing is happening when we see a rainbow. Sunlight is travelling through drops of water in the air and when the sunlight passes through, the light divides and shows the colors of the spectrum with each color having different wave lengths.

Of course, we now know that some animals and insects can see parts of the spectrum that humans cannot see, such as ultraviolet (UV) light.

spraying water makes a rainbow

Forensic scientists make use of UV light to show fingerprints, footprints and blood traces that are not normally seen with the naked eye.

Light will travel at different speeds through different substances, such as glass, water, and air. Air has the least resistance and light travels through air at about 300,000 kilometers per second.

The light we see from the sun travelled from the sun ten minutes before we see it.

planets-orbiting-sun

Light can behave like waves and particles. It has energy and can perform work but because light is always moving, it cannot be stored to be used later.

Light contains photons (particles) that contain energy and this energy can be transformed into other forms of energy.

photosynthesis for kids

For example, plants use sunlight to create chemical energy in photosynthesis.

There is no light in space because there is nothing the light can bounce off. We can only see the moon because it is reflecting the light of the sun. Fascinating, eh?

Now, try our quiz to test your knowledge on this cool topic!

quiz-time

Questions:

  1. What did Newton see when light passed through a glass prism?
  2. What mechanical device can be used to create light?
  3. What is ultraviolet light?
  4. Why is there no light in space?
  5. What is it called when plants use light to make chemical energy?

plant with bee

Answers:

  1. He saw that the light bent as it passed through a prism and divided into 7 visible colors.
  2. A mechanical way of seeing light is when a fire is produced or a battery attaches to a light bulb.
  3. Ultraviolet light is a light rays that is invisible to our naked eye.
  4. Light has to have something to bounce off of in order for it to be seen.
  5. Plants change light into chemical energy in photosynthesis.

Physics

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