Light, Colours, Quantum Theory

Light, Colours, Quantum Theory


Scientific study of light 
Ans : Optics
Light is an
Ans : Electromagnetic Wave & Transverse wave
It behaves as wave and particle. Thus light has dual nature
Light travels through air or vacuum at a speed of
Ans : 3 x 108m/s 
Order of speed of light
Ans : water < glass < air < vacuum 
Velocity of light is greater than the 
Ans : Sound
Light reaches earth from sun in
Ans : 8 minutes 20 seconds (500seconds) 
Substances which do not pass light through them are called 
Ans : Opaque substances 
eg : paper, stone
Substances which allow light to'pass through them are called
Ans : Transparent substances 
eg : glass 
Wave theory of light was proposed by 
Ans : Christiaan Huygens 
Electromagnetic theory of light was propsed by
Ans : James Clark Maxwell 
'The Corpuscular theory' related to light was proposed by
Ans : Isaac Newton in 1675 
The shadow obtained from a point source is a region of darkness which is called 
Ans : Umbra


Colour of any transparent object depends on the colour of the light transmitted by it 
Colour of any opaque object depends on the colour of light it reflects
Spectrum of white light -
Ans : Light consits of seven colours such as Violet, indigo, Blue, Green Yellow, Orange and Red (VIBGYOR)
The band of seven colours obtained due to the dispersion of white light is called 
Ans : Visible Spectrum
When frequency increases wave length 
Ans : Decreases
Deviation most through glass prism 
Ans : Red
Deviation least through glass prism 
Ans : Violet
Colour with maximum frequency 
Ans : Violet
Colour with minimum wavelength
Ans : Violet
Colour with maximum wavelength
Ans : Red
Colour with minimum frequency
Ans : Red
Colour used In laboratory for Indicating danger
Ans : Yellow
Colour sensitive to human eye 
Ans : Yellow
Colour used as danger signal 
Ans : Red




Corpuscular theory -  Isaac Newton
Wave theory  - Christiaan Huygens
Quantum Theory  - Max Planck
Electromagnetic theory - James Clark Maxwell
Photo electric effect - Heinrich Hertz
A white surface reflects all form's of light and heat
A black surface absorbs all forms of light and heat
Red light passing through a green object, appears
Ans : Black
Sky appears blue - Due to the shorter wavelength of blue colour, it is scattered more than the red colour of longer wavelength


Primary colours are
Ans : Red, Green, Blue
Primary colours used in colour television are
Ans : Red, Green, Blue 
Colour television uses
Ans : Additive colour mixing
By mixing suitable mixture of primary colours gives
Ans : Secondary colours 
eg : Magenta, Cyan, Yellow
Green  Red = Yellow
Blue  Red = Magenta
Green  Blue = Cyan 
Green  Blue  Red = White
The branch of physics which deals with the measurement of light emitted by objects is called
Ans : Photometry 
Tertiary colours:
Ans : Mixing up of two secondary colours


Complementary colours are the primary colours which give white colour when put together with the secondary colours
Green  Magenta -->White
Blue  Yellow -->White
Red  Cyan -->White
The substances used in colour paints, filters, plastics and other materials 
Ans : Pigments
Subtractive colour mixing is used in 
Ans : Pigments
For printing, colour pigments used are 
Ans : Yellow, Magenta, Cyan


The light rays consist of small energy packets called 
Ans : Quantum
Quantum of light is known as
Ans : Photon
Quantum Theory was put forward by
Ans : Max Planck
Absorption of light of one wave length by a substance and the re-emission of light of greater wavelength is called
Ans : Flourescence
Emission of light in the visible region after absorbing certain electromagnetic radiations is called
Ans : Photoluminescence

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