IB Physics

Option C – Lenses & Mirrors IV

Mr. Jean

The plan:

• Video clip of the day

• Refraction & dispersion

• Len & mirror videos

• Examples & Diagrams

• Convex mirror (spherical mirror)

Convex/converging Lens

parallel rays converge to the focal point

fif not parallel, they converge (image formed) at a different point

at each interface, Snell’s law is

satisfied

Where will image be formed?

focusfocus

The equation:

1 1 1

p q f

Ray diagram just like one for concave mirror, except rays continue to right instead of reflecting back!

positive q = right hand side of lens q

Mp

Magnification same:

Concave/diverging Lens

parallel rays seem to be coming from the focal point

f

Diverging lenses

virtual image!The equation:

1 1 1

p q f (negative f)

Negative q: means image on same side of lens as object (virtual)

Thick lenses and surfaces

1 2 2 1n n n n

p q R

1 2

1 1 11n

f R R

Lens-makers’ eqn:

Careful with signs!!! (see table 36.2)

Convex Mirror:

• An object is 15 cm from the surface of a reflective spherical Christmas-tree ornament 6cm in diameter.

• What is the position of the image?