OP MT2

• the angle turned through per unit length of arc
• R = 1/r in Dioptre (D)

Light passes through an interface b/t 2 optical media

Light bounces at interface

New wavefront curvature (vergence in air) L' gives distance to image

more vergence changing power

measures surface power by measuring the sag of a lens of a specific refrative index

elements positioned such that they have a common axis

• Measure of the ability of the surface to change the vergence of light
• Fs = (n'-n)/r = n'/f' = -n/f
• in Dioptre

ray passes through the center of curvature (it is undeviated because it is normal to the spherical surface)

has two refracting surfaces (both surfaces spherical or one surface may be plano (plane, no curvature, zero power))

Thickness at the vertex of the lens

negligible centre thickness, change in vergence as light passes through the lens is insignificant

both surfaces are have the same sign but different powers

both surfaces have the same power

center of curvature is on the same side of lens for both surfaces

zero power on one side, all power on other side

any power of lens can be obtained by a combination of surface powers

• Light from infinity (parallel) passes lens and focuses at the SECOND prinicipal focus
• Light emerging from FIRST principal focus emerges from the lens parallel

• closest possible distance b/t a real object and its real image in a plus lens
• OR
• closest possible distance b/t a virtual object and its virtual image in a minus lens

location of object and image when m=+1