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G8 Natural Science > visible light > Flashcards

visible light Flashcards

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1
Q

Light energy:

A
  • is emitted from luminous objects
  • reflects off some surfaces and object
  • is absorbed by certain surfaces
  • is refracted by transparent objects
  • is transferred by radiation
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2
Q

What are luminous objects

A
  • is a light source that radiates light energy

- eg.the sun,stars,candles

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3
Q

What are non luminous objects

A
  • are not a source of light energy itself, but it reflects the light of a luminous source
    eg. moon and planets
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4
Q

What is a propagation

A

-light moves in a straight line

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5
Q

What are the properties of image formed by the pinhole camera

A
  • the image is inverted (upside down)

- the image is real

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6
Q

What is radiation

A

-Light is radiated in a similar way to heat being radiated from a barbecue fire

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7
Q

How does light travel

A

-travels through empty spaces,which is why it is possible for rays of the sun to reach the earth

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8
Q

What is the spectrum of visible light

A

-it refracts white light into the colours of the spectrum

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9
Q

What are the colours of the dispersion

A
  • red
  • orange
  • yellow
  • green
  • blue
  • indigo
  • violet
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10
Q

How does a dispersion work

A
  • the prism refracts white light twice
  • at the first separation level it is refracted towards the normal
  • at the second separation level it is refracted away from the normal
  • after the second refraction of white light the complete spectrum is visible
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11
Q

What is normal

A
  • the perpendicular line (90’) to the surface where the light ray hits the surface.
  • It is necessary to use the normal because not all surfaces are flat
  • It is difficult then to measure angles accurately
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12
Q

What differs from the prism every colour emerging

A
  • the angle
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13
Q

The angle of a prism differs, this means

A

-that every colour moves through the prism at a different velocity

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14
Q

What happens with violet

A
  • has the most energy
  • highest frequency
  • shortest wave length
  • light is refracted the most
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15
Q

What happens with Indigo

A
  • slightly less energy
  • slightly lower frequency
  • longer wave length
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16
Q

What happens with red

A
  • with the least energy
  • lowest frequency
  • longest wave length
  • red light is refractured the least
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17
Q

What is transparent substances

A
  • allow most of the light through and you cans through it
  • reflects some of the light
  • absorb some of the light
    eg. clear glass,plastic, clean water
18
Q

What is translucent

A

-allow light through, but you can not see through it

eg matt glass

19
Q

What is opuque

A

-do not allow light through and you cannot see through it
eg metal and wol
-they:
-absorb or reflect light
-cause shadows on the sides away from the light source

20
Q

What is absorption

A

-light energy is absorbed differently by different objects

21
Q

What happens with transparent coloured objects

A

-when red light and green light, respectively, fall on a red filter, only the red light is let through
The red filter absorbs all other colours and allows only red light through, same with green

22
Q

What happens with opaque objects

A

-absorb all other colours and only reflects the colour of the object
-only this reflected colour reaches your eyes that is the colour of the object
eg. white light on red paper=red light
red light on red paper=red light

23
Q

What is reflection

A
  • objects that are not luminous, can only be seen when light is reflected off it
  • therefore light rays must sine on the object
  • most surfaces reflect light
    eg. light rays from the sun
24
Q

What is a smooth surface

A
  • with reflection, the angles of incidence and reflection are equal
  • the angle of incidence is between the incident rays and the normal
  • the angle of reflection is between the reflection ray and the normal
    eg. a mirror reflect same direction
25
Q

What is normal

A

-is line perpendicular to the level between the glass and air

26
Q

What is rough surfaces

A
  • if an object has a rough surface it is also not smooth on microscopic
  • when light shines on a rough surface, the light rays are not all reflected in the same direction
  • the reflected light is scatted
27
Q

What is observation

A
  • some colours of the spectrum (some frequency ) are absorbed and some colours are reflected
    eg. A blue car looks blue because the colour frequency of violet, indigo, green, yellow, orange, and red are absorbed and only blue is reflected
28
Q

What can green plants do

A

They can photosynthesis due to the presence of chlorophyll, a green pigment

29
Q

What does chlorophyll do

A

-absorbs sunlight, and via the process os photosynthesis transforms light energy into chemical potential energy

30
Q

How do we see light

A

-the black spot in the centre of the eye is actually a opening,the pupil, where light enters the eye

31
Q

What is the retina

A

-it is at the back of the eyeball, operates like a screen onto which the lens projects the image

32
Q

What does the retina contain

A

-specialised receptor cells which are simulated by specific colour/frequencies

33
Q

What does optic nerve transfer

A

-the impulses to the brain for interpretation

34
Q

What is the path of a light rays in the eye

A

light -pupil-light-lens -light -retina -electrical impulse -optic nerve -electrical impulse - brain

35
Q

What don’t reach the eye

A

-the frequencies of light theatre absorbed by the surface of an object

36
Q

What happens when light rays strikes a rectangular transparent or translucent objects

A

-the light ray is refracted towards the normal

37
Q

What happens if the light rays moves out of the glass

A
  • refracts away from the normal

- pg 238 NB!!!

38
Q

What are optometrist and what do they do

A
  • are health workers who specialise in optometry

- they improve peoples sight with glasses or operations ,needed tertiary studying

39
Q

What is photography

A
  • is a form of art, but is also a science
  • light rays, light sensitive media,photographic films and electronic image censors are used
  • properties of light such as motion in straight lines, reflection and absorption are applied in this career
40
Q

What is astronomy

A
  • study of the solar systems
  • the use and applications of lenses form a major part of these studies
  • careers in this flied require tertiary education
41
Q

what is careers with optic fibres

A

-use of optic fibres made a huge difference in telecommunication
-involves installation, maintenance and repair of optic
fibres
-training is done at technical schools and collages

G8 Natural Science (2 decks)

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