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VISIBLE LIGHT
EM SPECTRUM: VISIBLE LIGHT
VISIBLE LIGHT
❏A very small part of the Electromagnetic Spectrum that is visible to the human eye.
Wavelength: 380 - 700 nm Frequency: 400 - 790 THz
FACTS
❏The color of light emitted by stars can teach scientists a lot about them. The color of a star's light indicates its temperature and the types of gasses it is composed of.
❏We also use visible light to study our own sun's structure. Satellites equipped with visible-light cameras are constantly
used to study and monitor the Earth's surface.
❏There are actually “combinations” to making visible light. Like mixing infrared light with UV light will make visible light. But it needs to be mixed in what’s called a non-linear material. This is called “nonlinear optics mixing”.
EXAMPLES
❏ Sunlight
The light that we receive from the sun is a prominent example of visible light in real life.
❏ Moonlight
Moon does not have its own light, but it reflects the sunlight into the surroundings and therefore, is known as the secondary or reflective source of light. This means that the light reflected by the moon is also an example of visible light in real life.
❏ Lasers
LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation. LASER is a device that produces a high intensity, narrow beam of visible light through a process of optical amplification that is based on the stimulated emission of electromagnetic radiations.
PHOTORECEPTORS
❏Born on Jan. 4, 1643 , in Woolsthorpe, Lincolnshire, Eng.
❏Died on March 31, 1727 , in London.
❏He was educated at Cambridge University (1661–65), where he discovered the work of René Descartes. (Rene Descartes made solving geometric problems using algebraic equations possible).
❏He discovered the heterogeneous, corpuscular nature of white light and laid the foundation of physical optics.
Newton began his investigations by cutting a pinhole in his window shade to let in sunlight, which showed up on his wall as a round illuminated area.
Refracted by a prism, it turned into an oblong area with a rainbow of colors. Intrigued by the change in shape, Newton cut a variety of holes of different sizes and shapes, but no matter the shape of the original beam, the refracted light turned more oblong.
Newton also placed a second prism of the same type in the path of the light and was able to turn the colors back into white light. This showed that white light, rather than being pure, was composed of a miscellany of colors.
USES OF VISIBLE LIGHT
ISAAC NEWTON
❏Visible light is extremely important to humans because we use it to see.
❏We concentrate visible light to make lasers to use in everything from surgery, to CD players to laser pointers.
❏Visible light waves also make our TV, computer and cell phone screens work.
❏Plants use light to power their photosynthesis.
DANGERS OF VISIBLE LIGHT
❏Generally speaking, visible light is quite safe. But some light can be so strong that it harms your eye's receptor cells, which can lead to temporary or permanent blindness.
❏ Burns can be caused by high power lasers, which can also be harmful.
❏Digital devices like LED screens are examples of what can cause blurred vision, eye fatigue, and long-term vision issues like nearsightedness.
❏Visible light radiation can cause erythema, pigmentation, thermal damage, and free radical production , among other things.
WAYS TO AVOID OR MINIMIZE DANGER/RISKS
❏Glass
Standard glass filters out UVB , but transmits longer wavelengths of radiation: UVA, visible light and infrared.
❏Sunblock
Sunscreens are the mainstay of treatment for photodermatoses (a group of cutaneous disorders characterized by an abnormal reaction to light exposure). UV filters are divided into organic (also known as chemical) and inorganic (also known as physical) filters;
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