visible light Flashcards
Light energy:
- 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
What are luminous objects
- is a light source that radiates light energy
- eg.the sun,stars,candles
What are non luminous objects
- are not a source of light energy itself, but it reflects the light of a luminous source
eg. moon and planets
What is a propagation
-light moves in a straight line
What are the properties of image formed by the pinhole camera
- the image is inverted (upside down)
- the image is real
What is radiation
-Light is radiated in a similar way to heat being radiated from a barbecue fire
How does light travel
-travels through empty spaces,which is why it is possible for rays of the sun to reach the earth
What is the spectrum of visible light
-it refracts white light into the colours of the spectrum
What are the colours of the dispersion
- red
- orange
- yellow
- green
- blue
- indigo
- violet
How does a dispersion work
- 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
What is normal
- 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
What differs from the prism every colour emerging
- the angle
The angle of a prism differs, this means
-that every colour moves through the prism at a different velocity
What happens with violet
- has the most energy
- highest frequency
- shortest wave length
- light is refracted the most
What happens with Indigo
- slightly less energy
- slightly lower frequency
- longer wave length
What happens with red
- with the least energy
- lowest frequency
- longest wave length
- red light is refractured the least
What is transparent substances
- 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
What is translucent
-allow light through, but you can not see through it
eg matt glass
What is opuque
-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
What is absorption
-light energy is absorbed differently by different objects
What happens with transparent coloured objects
-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
What happens with opaque objects
-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
What is reflection
- 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
What is a smooth surface
- 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
What is normal
-is line perpendicular to the level between the glass and air
What is rough surfaces
- 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
What is observation
- 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
What can green plants do
They can photosynthesis due to the presence of chlorophyll, a green pigment
What does chlorophyll do
-absorbs sunlight, and via the process os photosynthesis transforms light energy into chemical potential energy
How do we see light
-the black spot in the centre of the eye is actually a opening,the pupil, where light enters the eye
What is the retina
-it is at the back of the eyeball, operates like a screen onto which the lens projects the image
What does the retina contain
-specialised receptor cells which are simulated by specific colour/frequencies
What does optic nerve transfer
-the impulses to the brain for interpretation
What is the path of a light rays in the eye
light -pupil-light-lens -light -retina -electrical impulse -optic nerve -electrical impulse - brain
What don’t reach the eye
-the frequencies of light theatre absorbed by the surface of an object
What happens when light rays strikes a rectangular transparent or translucent objects
-the light ray is refracted towards the normal
What happens if the light rays moves out of the glass
- refracts away from the normal
- pg 238 NB!!!
What are optometrist and what do they do
- are health workers who specialise in optometry
- they improve peoples sight with glasses or operations ,needed tertiary studying
What is photography
- 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
What is astronomy
- 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
what is careers with optic fibres
-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
