Huygens construction definition
Each part of a wavefront is like a point source of tiny circular waves and these wavelets add up to give a wavefront one wavelength away
The two laws of reflection
- When light is reflected, the incident ray, the reflected ray and the normal all lie in the same plane
- The angle i between the incident ray and the normal = the angle r between the reflected ray and the normal
If a medium is denser then the light…
Slows down and bends towards normal
Angle i > Angle r
New medium is denser
Angle i < Angle r
Old medium is denser
Snells law in words
Constant = sin (angle of incidence,i) / sin (angle of refraction,r)
Snells law as an equation
n = sin i / sin r
What is the constant n
Refractive index
Refractive index equation with speed of light
n = speed of light in vacuum / speed of light in medium
Refractive index of air
1
Light going from one medium to another
n2 / n1 = sin1/sin2
Does the angle of incidence affect angles of refraction
Yes the smaller the angle i, the bigger the angle r
What is the critical angle
The largest angle at which refraction out of a denser medium is just possible
Snells law for critical angle
n = 1 / sinC
What is n in Snells law for critical angle
Refractive index of original medium
What is partial internal reflection
Angle i < Critical angle so some part if the ray is reflected and some is refracted
What is total internal reflection
Angle i > Critical angle so no light is refracted and all is reflected
Optical fibres
The angle that the ray means the normal to the surface is always much more than the critical angle so the ray is internally reflected
Convex lens shape
Oval
Is the principle focus before or after the Convex lens
After
Is the principle focus before or after the Concave lens
Before
Focal length definition
The distance from its middle to the principle focus F
Will a more powerful lens have a shorter on longer focal length
Shorter
Will a weaker lens have a shorter on longer focal length
Longer
