Light and Colour

Question 1

Is light a wave or a particle?

Answer 1

light is both a wave And a particle (wave - particle duality)

Question 2

What are the hues/colours of visible light

Answer 2

Red, Orange, Yellow, Green, Blue, Violet (ROYGBV)

Question 3

What colours make up white light

Answer 3

All of them

Question 4

Put these in order of wavelength from longest to shortest:

Microwaves, Radio Waves, infrared, Gamma rays, X-rays, Visible light, Ultraviolet light

Answer 4

Radio
Microwave
Infrared
Visible Light
Ultraviolet
X-ray
Gamma Rays

Question 5

Longer wavelength = _____ frequency

Answer 5

Longer wavelength = lower frequency

Question 6

Higher frequency waves have ____ wavelengths

Answer 6

Higher frequency waves have shorter wavelengths

Question 7

What is the frequency wavelength range of visible light

Answer 7

720nm - 380nm

Question 8

Red light has a ____ frequency than Ultraviolet light

Answer 8

Red light has a lower frequency than Ultraviolet light

Question 9

Higher Amplitude = ____ colours

Answer 9

Higher Amplitude = brighter colours

Question 10

What type of waves have wavelengths on the scale of humans - buildings

Answer 10

Radio Waves

Question 11

Infrared has a ____ frequency and ____ wavelength than visible light

Answer 11

Infrared has a lower frequency and longer wavelength than visible light

Question 12

Ultraviolet light (UV) has a ____ frequency and ____ wavelength than visible light

Answer 12

Ultraviolet light (UV) has a higher frequency and shorter wavelength than visible light

Question 13

Define Reflection

Answer 13

Reflection is when the wave hits a surface and bounces off and
no radiation absorbtion

Question 14

Define Refraction

Answer 14

Refraction is when the wave hits another medium at an angle and bends

Question 15

What determines the angle during refraction?

Answer 15

The refraction index

Question 16

Define Diffraction

Answer 16

Diffraction is when the wave bends around a barrier and spreads at oblique angles
OR interacts with edges of an opening

Question 17

light waves are ____ in all planes to the direction they are going

Answer 17

light waves are perpendicular in all planes to the direction they are going

Question 18

Define interference

Answer 18

Interference I when two or more waves superpose to form a resultant wave

Question 19

What is destructive interference?

Answer 19

Destructive interference is when out of phase waves superpose and give a lower resultant amplitude

Question 20

What is meant by “out of phase”?

Answer 20

When troughs of one wave occur at crests of the other

Question 21

What is constructive interference?

Answer 21

When the resultant wave has higher amplitude. The amplitude is given by the sum of both

Question 22

“To see colour there needs to be a ____, and ____ to interact with light and the eye”

Answer 22

“To see colour there needs to be a source, and object to interact with light and the eye”

Question 23

What do polarisers do?

Answer 23

Polarisers restrict polarisation (select one direction)

Question 24

What are additive colours?

Give examples

Answer 24

Colours seen directly

eg. Primary colours from screens (Red, Green, Blue, i.e RGB )

Question 25

How do subtractive colours work?

Answer 25

Light interacts with/ hits an object | One colour is absorbed and the complimentary is reflected and then observed

Question 26

What are the complimentary colours of red, green and blue (i.e when red is absorbed what is reflected)

Answer 26

Red: Cyan ( =blue+green) Green: Magenta (=red+blue) Blue: Yellow (=red+green)

Question 27

Where is subtractive colour mixing used

Answer 27

In dyes and pigments

Question 28

What is fluorescence?

Answer 28

Fluorescence is a form of luminescence where light is emitted by a substance that has absorbed light or other electromagnetic radiation

Question 29

How much energy, E, are photons are emitted with during florescence ?

Answer 29

E = hf

Question 30

What are h and f in E = hf?

Answer 30

``` h = plank's constant f = frequency ```

Question 31

Explain Stokes Shift

Answer 31

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)

Question 32

What is the main difference between fluorescence and phosphorescence?

Answer 32

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.

Question 33

Stokes Shift: Emitted light has ___ energy than absorbed light

Answer 33

Emitted light has less energy than absorbed light