Light
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Where does light come from?
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In this video we learn all about Light. We learn where it comes from and identify a number of sources of light. We also learn how we can change light through reflection, refraction, or by blocking light all together.
Light is a form of energy. The Sun is a very important source of light energy.
Without the energy from the Sun, there would be no plants or animals on Earth's surface.
We can see because of light. Most light can be found in nature, like the sun, while other light sources are created by people, such as flashlights and lasers. Light is a form of energy that moves in straight lines. We see objects when they give out light, or reflect it, into our eyes. Our eyes are able to process this light and turn it into an image in our brain.
Lack of sunlight
When a lack of sunlight keeps us from sleeping well and causes us to become vitamin D deficient, our immune system can suffer, and we may get sick more frequently. Vitamin D deficiency has been found to make us more susceptible to colds and the flu, as well as infection and autoimmune disorders.
Light & human life?
Light is essential to our health and wellbeing; it regulates our sleep-wake cycle. It can also help with our daily routines: from bright functional light to keep you energized and up your concentration level, to warm light that creates a cozy ambiance that helps you to unwind in the evening.
What is the importance of light?
Light is responsible for all life, for the production of the air that we breathe, the cycles of our oceans, the magnetic fields around our planet, gravity, warmth and our weather. We omit the importance of the true nature of the projection of our sun at our peril.
Vision: Light is essential for vision. When light hits the retina at the back of the eye, it is converted into electrical signals that are sent to the brain. The brain then interprets these signals to create the images that we see.
Circadian rhythm: Light exposure helps to regulate our circadian rhythm, which is our internal clock that controls our sleep-wake cycle. When we are exposed to light during the day, it helps to suppress the production of melatonin, a hormone that makes us feel sleepy. In contrast, when we are exposed to darkness at night, melatonin levels rise, which helps us to fall asleep.
Mood and energy levels: Light exposure can also affect our mood and energy levels. Exposure to bright light during the day can help to improve our mood and energy levels, while exposure to darkness at night can help to promote relaxation and sleep.
Cognitive function: Light exposure can also affect our cognitive function. Exposure to bright light during the day can help to improve our attention, memory, and reaction time. In contrast, exposure to darkness at night can impair our cognitive function.
Light travels in waves, but it also behaves like a particle. This is called the wave-particle duality of light.
Light waves are transverse waves, meaning that the vibrations are perpendicular to the direction of travel. This is different from longitudinal waves, like sound waves, where the vibrations are parallel to the direction of travel.
Light waves travel at the speed of light, which is about 300,000 kilometers per second (186,000 miles per second). This is the fastest speed anything in the universe can travel.
Light waves can travel through a vacuum, which is empty space. This is why we can see the sun and stars, even though there is no air in space.
Light travel in Waves
Imagine you drop a pebble into a pond. The pebble creates ripples that travel across the surface of the pond. These ripples are like light waves. They travel in all directions from the source (the pebble) and they can be reflected, refracted, or absorbed.
Light behave like Particles
This experiment shows that light can interfere with itself like a wave, but it is also detected as individual particles.
Imagine a pool of water with two narrow slits in it. When you shine light through the slits, the light waves interfere with each other, creating a pattern on the screen behind the slits. This pattern is similar to the pattern created by water waves when they pass through two narrow openings.
However, if you dim the light so that only one photon is passing through the slits at a time, the light is still detected as individual particles on the screen. This suggests that light has both wave-like and particle-like properties.
When light waves travel through a material, they can be reflected,
refracted, absorbed, or diffracted.
Reflection is when light waves bounce off of a surface. This is what happens when you see your reflection in a mirror.
Reflection in a mirror: When light hits a mirror, it is reflected back at the same angle. This is why we can see our reflection in a mirror.
Reflection in water: When light hits water, it is partially reflected and partially refracted. The amount of light that is reflected depends on the angle of the light and the smoothness of the water surface. This is why we can see our reflection in water, but it is not as clear as our reflection in a mirror.
Refraction is when light waves bend as they pass from one material to another. This is what happens when you see a straw look bent in a glass of water.
Sundog: Sundogs are two bright spots that can be seen in the sky, one on either side of the Sun. Sundogs are caused by the refraction of light through ice crystals in the atmosphere.
Light pillars: Light pillars are vertical beams of light that can be seen rising from the Sun or Moon. Light pillars are caused by the reflection of light from ice crystals in the atmosphere.
Absorption is when light waves are converted into heat energy. This is what happens when you wear a black shirt on a hot day.
Chlorophyll in plants: Chlorophyll is a green pigment that absorbs sunlight and uses it to convert carbon dioxide and water into sugar and oxygen. This process is called photosynthesis and it is essential for life on Earth.
Melanin in skin: Melanin is a pigment that gives skin its color and it also protects the skin from the harmful UV rays of the sun. Melanin absorbs UV rays and converts them into heat, which is then released from the body.
Diffraction is when it spreads out as it passes through a narrow opening or around a sharp edge. This is what causes rainbows and the diffraction patterns you see when you shine a laser through a grating.
Butterfly wings: The wings of many butterflies are covered in tiny scales that diffract light, producing iridescent colors.
Sea shells: The surfaces of many sea shells are covered in tiny ridges that diffract light, producing iridescent colors.
Here is a simple analogy to help you understand how light travels:
Imagine a pond with a pebble thrown into it. The pebble creates ripples that travel across the surface of the pond. The ripples are like light waves. They travel in all directions from the source (the pebble) and they can be reflected, refracted, or absorbed.
If you hold a stick in the water, the ripples will bend around the stick. This is like refraction.
If you put a rock in the water, it will absorb the ripples. This is like absorption.
How does light move?
Plants are green in colour because
(a) They absorb green light only.
(b) They reflect green light.
(c) They absorb green light but reflect all other lights.
(d) None of these.
So, the correct answer is, ‘they reflect green light.’
Light is made up of many colours.
These colours can be seen when light is broken up.
When light falls on the plant some amount of wavelength is absorbed by the chlorophyll and accessory pigments.
Because of the nature of these pigments only the green wavelength is reflected by the plant.
The reflected wave when falling into our eyes then our eyes which consist of light- sensitive photoreceptors identifies the colour and interprets it to the brain.
What is a light year?
A light-year is the distance light travels in one year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!
What is the speed of light?
The speed of light is 299,792,458 metres per second, or about 186,282 miles per second.
In fact, light has different properties, which means it behaves in different ways depending on the type of object that it hits.
It can be:
Reflected
Transmitted
Refracted
Absorbed
Refraction: When light passes from one medium to another, it bends. This is called refraction. You can see refraction in rainbows, when the light from the sun bends as it passes through the water droplets in the a
Transmission: When light hits an object, some of the light passes through the object. The amount of light that passes through depends on the properties of the object. For example, a piece of clear glass will transmit most of the light that hits it, while a piece of opaque cardboard will transmit very little l
Absorption: When light hits an object, some of the light is absorbed by the object. The color of the object depends on the wavelengths of light that it absorbs. For example, a red apple absorbs all of the wavelengths of light except for red, so it appears red to
Visible Spectrum
The visible spectrum is the part of light (the portion of the electromagnetic spectrum) that is visible to the human eye. It ranges in wave length from approximately 400 nanometers (which is violet) to 700 nm (which is red).
The colors in order from shortest wavelength to longest wavelength, are:
Violet, Blue, Green, Yellow, Orange, Red
Non-Visible Spectrum
The non-visible spectrum is the part of light (the portion of the electromagnetic spectrum) that is not visible to the human eye.
Here are some examples of non-visible light:
Ultraviolet light: Ultraviolet light is used to sterilize medical equipment and to tan skin.
Infrared light: Infrared light is used in night vision goggles and to control remote controls.
X-rays: X-rays are used to take pictures of bones inside the body.
Gamma rays: Gamma rays are used to treat cancer and to sterilize food.
Wave Length Of Light
What is light and its uses?
Light is the sole source of food generation for all living organisms on the earth. Almost all living beings depend on light for their food and energy. Plants and other autotrophs synthesize their own food materials by use of light. The light which falls on the leaves of a plant is trapped.Apr 1, 2020
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.
Vision: Light energy is essential for vision. When light hits the retina at the back of the eye, it is converted into electrical signals that are sent to the brain. The brain then interprets these signals to create the images that we see.
Plant growth: Plants use light energy to convert carbon dioxide and water into glucose, a type of sugar. This process is called photosynthesis. Glucose is then used by plants for energy and to build other molecules.
Solar power: Solar power is a form of renewable energy that uses light energy from the sun to generate electricity. Solar panels convert sunlight into electricity, which can then be used to power homes, businesses, and other buildings.
Medical imaging: Light energy is used in medical imaging techniques such as X-rays, MRI, and ultrasound. These techniques allow doctors to see inside the body without surgery.
Communication: Light energy is used in telecommunications, such as fiber optic cables and lasers. These technologies allow for the transmission of data over long distances at high speeds.
Examples of the uses of light energy
Lasers: Lasers are devices that use light energy to create a beam of light. Lasers are used in a variety of applications, including surgery, manufacturing, and telecommunications.
Artificial lighting: Light energy is used in artificial lighting to provide light in places where there is no natural light. Artificial lighting is used in homes, businesses, and other buildings.
Telecommunication: Light energy is used in telecommunications to transmit data over long distances. Fiber optic cables use light to transmit data at high speeds.
Security systems: Light energy is used in security systems to detect movement. For example, motion sensors use light energy to detect movement and trigger an alarm.
Security systems using light energy
Medical diagnostics: Light energy is used in medical diagnostics to examine the inside of the body. For example, X-rays use light energy to create images of bones and other tissues.
What is radiation good for? Some examples
Health: thanks to radiation, we can benefit from medical procedures, such as many cancer treatments, and diagnostic imaging methods.
Energy: radiation allows us to produce electricity via, for example, solar energy and nuclear energy.
Environment and climate change: radiation can be used to treat wastewater or to create new plant varieties that are resistant to climate change.
Industry and science: with nuclear techniques based on radiation, scientists can examine objects from the past or produce materials with superior characteristics in, for instance, the car industry.
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