Light and Colour Flashcards
Is light a wave or a particle?
light is both a wave And a particle (wave - particle duality)
What are the hues/colours of visible light
Red, Orange, Yellow, Green, Blue, Violet (ROYGBV)
What colours make up white light
All of them
Put these in order of wavelength from longest to shortest:
Microwaves, Radio Waves, infrared, Gamma rays, X-rays, Visible light, Ultraviolet light
Radio Microwave Infrared Visible Light Ultraviolet X-ray Gamma Rays
Longer wavelength = _____ frequency
Longer wavelength = lower frequency
Higher frequency waves have ____ wavelengths
Higher frequency waves have shorter wavelengths
What is the frequency wavelength range of visible light
720nm - 380nm
Red light has a ____ frequency than Ultraviolet light
Red light has a lower frequency than Ultraviolet light
Higher Amplitude = ____ colours
Higher Amplitude = brighter colours
What type of waves have wavelengths on the scale of humans - buildings
Radio Waves
Infrared has a ____ frequency and ____ wavelength than visible light
Infrared has a lower frequency and longer wavelength than visible light
Ultraviolet light (UV) has a ____ frequency and ____ wavelength than visible light
Ultraviolet light (UV) has a higher frequency and shorter wavelength than visible light
Define Reflection
Reflection is when the wave hits a surface and bounces off and
no radiation absorbtion
Define Refraction
Refraction is when the wave hits another medium at an angle and bends
What determines the angle during refraction?
The refraction index
Define Diffraction
Diffraction is when the wave bends around a barrier and spreads at oblique angles
OR interacts with edges of an opening
light waves are ____ in all planes to the direction they are going
light waves are perpendicular in all planes to the direction they are going
Define interference
Interference I when two or more waves superpose to form a resultant wave
What is destructive interference?
Destructive interference is when out of phase waves superpose and give a lower resultant amplitude
What is meant by “out of phase”?
When troughs of one wave occur at crests of the other
What is constructive interference?
When the resultant wave has higher amplitude. The amplitude is given by the sum of both
“To see colour there needs to be a ____, and ____ to interact with light and the eye”
“To see colour there needs to be a source, and object to interact with light and the eye”
What do polarisers do?
Polarisers restrict polarisation (select one direction)
What are additive colours?
Give examples
Colours seen directly
eg. Primary colours from screens (Red, Green, Blue, i.e RGB )
How do subtractive colours work?
Light interacts with/ hits an object
One colour is absorbed and the complimentary is reflected and then observed
What are the complimentary colours of red, green and blue (i.e when red is absorbed what is reflected)
Red: Cyan ( =blue+green)
Green: Magenta (=red+blue)
Blue: Yellow (=red+green)
Where is subtractive colour mixing used
In dyes and pigments
What is fluorescence?
Fluorescence is a form of luminescence where light is emitted by a substance that has absorbed light or other electromagnetic radiation
How much energy, E, are photons are emitted with during florescence ?
E = hf
What are h and f in E = hf?
h = plank's constant f = frequency
Explain Stokes Shift
Light of a certain Wavelength is absorbed
Excitation of electrons to higher energy levels
Energy is released i.e heat and light (photons)
Electrons return to ground state
Light is emitted at a higher wavelength (lower frequency)
What is the main difference between fluorescence and phosphorescence?
Fluorescence: emission is immediate and therefore only visible if the light source is continuously on
Phosphorescent material: Stores the absorbed light for some time and releases light later; an afterglow persists for a few seconds after the light has been switched off.
Stokes Shift: Emitted light has ___ energy than absorbed light
Emitted light has less energy than absorbed light
