Facts about Light

Facts to Remember
The speed of light in vacuum is 186,000 miles per second or 300,000,000 m/s
The speed of light is slower in transparent mediums like water, glass and air and depends upon the refractive index of the medium.
Light is the visible part of electromagnetic spectrum and the frequency of light lies between 4 x 1014 Hz to 8 x 1014 Hz
Colour of light with smallest wavelength is Violet with a wavelength of about 400 nanometers
Colour of light with longest wavelength is Red with a wavelength of about 650 nanometers
The study of properties and behaviour of light is known as Optics
Sunlight takes 8 minutes and 20 seconds to reach the Earth.
Light takes about 1.3 seconds to travel from the Earth to the Moon.
Three dimensional imaging using interference of light is known as Holography
System of light excitation used in surgeries, printers etc. is LASER
The colour of light which is most conducive to photosynthesis is Blue

Phenomenon of Light - Visible Effects

Phenomenon Visible Effect
Refraction of light
  • Day is lengthened
  • Stars appear to twinkle
  • Mirages are formed
  • Sun or moon appears larger in size when at horizon
  • Stick immersed in water appears bent at the point of separation
  • A person standing inside water appears shorter
Dispersion of lightRainbows are formed
Interference of lightBeautiful colours are seen in soap bubbles and oil films on water
Scattering of light rays of small wavelengthsSky appears blue
Sun appears red during sunrise and sunset


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Fill in the blanks – Facts about light

1. The speed of light in vacuum is m/s

2. The colour of light with the smallest wavelength is

3. The study of properties and behaviour of light is known as

4. Rainbows are caused due to of light.

5. Sunlight takes minutes seconds to reach the Earth.

6. The colour of light with the longest wavelength is

7. The colour of light which is most conducive to photosynthesis is .