Geometrical optics Flashcards
How are objects visible to us?
Objects are a source of light
light is reflected from the object
Speed of light in a vacuum
5 -1
3 x 10 m.s
Speed of light is … In a vacuum
constant
Light waves transmit
Energy
Sound waves need what to travel
Material medium
Light waves need a medium?
No they don’t need a material medium
Optical density measures
How easy it is for light to travel through a medium
High optical density =
Slower light waves
Spend waves vs light waves
Material medium
Light travels at constant velocity of …
8 -1
3 x 10 m.s
Light slows when traveling through … X3
Water
Glass
Perspex
Velocity and wavelength change but never
Frequency
Velocity
Speed (m.s -1)
When does light Ray only slow down but not bend?
When it enters a more optically dense medium at 90 degrees. The Ray is perpendicular to the surface of the object it travels through.
Refraction results in (in terms of true and apparent depth)
Optical illusions
Refraction definition
The bending of light when it travels from one material into another in which it has a different velocity
Rules of reflection
- Angle of incidence = angle of reflection
2. Incident, reflected Ray and the normal lie on the same plane
Normal
Line perpendicular to the surface
Incident Ray || x
Incident Ray || emergent Ray
Triangular prism explanation
Light entering Perspex block undergoes refraction.
Ray bends towards normal at the point where it enters and bends away where it leaves the prism.
Ray bends towards normal under what conditions…
Ray enters medium where speed of light is slower
Angle of deviation =
Incident Ray | ANGLE OF DEFLECTION | Emergent Ray
Focal point
Where the light rays cross/meet
Air RI
1,0003
Water RI
1,33
Plastic RI
1,46
Perspex RI
1,50
Glass RI
1,52
Diamond RI
2,42
Speed of light in vacuum
Speed of electromagnetic waves
C = 3 x 10 ^8 m.s -1
In transparent objects speed is …. In relation to vacuum
LESS
Refractive index
Speed of light in air
Refractive Index = ———————————–
Speed of light in the medium
n = c/v
Refractive index is never less than…
1
Relationship between optical density and refractive index
Directly proportional
Snells law
n1 sin ➰1 = n2 sin ➰2
➰1 is angle of incidence
➰2 is angle of refraction
n are the respective refractive indices
Critical angle
Angle of incidence that provides an angle of refraction of 90 degrees and the refracted Ray is parallel to the boundary between two media.
Speed of light in a vacuum
5 -1
3 x 10 m.s
Speed of light is … In a vacuum
constant
Light waves transmit
Energy