Light

Light

 

 

Units pages 65 to 71 in tables. Conversion factors page 45. Physical constants pages 46 & 47


 

Light.

Laws of reflection: I, r, and normal all in the same plane.

Angle of incidence = angle of reflection ( i = r)


 

Parallax = the apparent movement of an object due to the motion of an observer.


 

Real image = The actual intersection of rays of light. The image can be produced on a screen.

Virtual image = Apparent intersection of light. Image cannot be produced on a screen.


 

Refraction = The bending of rays of light as they pass from one medium to another.


 

Laws of refraction = I, r and normal all in the same plane.

Snell's law: n = sin i/sin r

Critical angle = The angle of incidence who's corresponding angle of refraction is 90 degrees.


 

Total internal reflection = When the incident angle exceeds the critical angle the ray of light does not pass out of the first medium but is reflected back into it. Application: Fibre optic cables.


 

For mirrors:

If object is outside focus in concave mirror the image is real. Ergo, inside f = imaginary

The image is always virtual and diminished in a convex mirror.


 

For Lenses.

If object is outside focus in convex lens the image is real. Ergo, inside f = virtual.

The image is always virtual and diminished in a concave lens.


 

The power of a lens is measured in m-1 (per metre)


 

The eye (labels): Lens, retina, iris, ciliary muscle, pupil, optic nerve.


 

Short sight = sees near objects, image focused short of retina. (Long sighted opposite obviously).


 

All formulae for light available pages 59 & 60 of tables.