Mirrors and Lenses Pinholes pinhole can be used

Mirrors and Lenses

Pinholes pinhole can be used to form an image • A ____ without a lens or mirror. Light rays from point source screen

Image formation with a Pinhole camera Light source Dark room = Camera fuzzy if pinhole is larger Image is ________ sharper if pinhole is smaller Image is _____ dimmer is pinhole is smaller

• How does light interact with pinholes? • How does light interact with lenses? Refraction – ______ • How does light interact with mirrors? Reflection – ______ We can use the _______. photon model

Mirrors • Flat • Concave • Convex

• The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at the same angle it hits it. The same !!!

Clear vs. Diffuse Reflection • Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions

The Law of Reflection incident angle qi equals For reflection the _______ reflected angle qr: the ________ qi = qr The angles are measured relative to the _____, normal shown here as a dotted line.

Forming Images with a Plane Mirror plane A mirror is an object that reflects light. A _______ mirror is simply a flat mirror. Consider an object placed at point P in front of a plane mirror. An image will be formed at point P´ behind the mirror. do = distance from object to mirror di = distance from image to mirror ho = height of object hi = height of image For a plane mirror: do = -di and ho =hi ho do di hi

Images An image is formed at the point where the rays of light leaving a single point on an object actually intersect or either _____ appear to from where they ____ originate.

Images • If the light rays actually do intersect, then the image is a _____. real image If the light only appears to be coming from a point, but is not physically there, then the image is a virtual image _______.

spherical A _____ mirror has _______ a surface shape with radius of curvature R. There are two types of spherical mirrors: concave _______ and convex _______. Spherical Mirrors ____ concave ____ convex

Focal Point When ____ parallel rays (e. g. rays from a distance source) are incident upon a spherical mirror, the reflected rays ____ intersect at the _____ focal point F, a distance R/2 from the mirror. For a ____ concave mirror the focal _______, point is in front of the mirror (_____). real

Focal Point For a ______, convex mirror the focal point is behind the The incident rays ______ diverge virtual mirror (____). from the _______ convex _______, mirror but they trace back to the focal point F.

Focal Length focal length (f) the distance from The ________is the surface of the mirror to the focal point. It can be shown that the focal length is half the radius of curvature of the mirror. Sign Convention: the focal length is negative if the focal point is behind the mirror. For a concave mirror, f = ____ ½R R (R always +) For a convex mirror, f = ½ ___

Lenses • Concave • Convex –Refraction

Reflection and Refraction When a light ray travels from one medium to reflected another, part of the incident light is _____ transmittedat the boundary part of the light is _______ between the two media. refracted The transmitted part is said to be _____ in the second medium. incident ray reflected ray refracted ray

Red Light

Lenses Light is reflected from a mirror. Light is _____ refracted through a lens.

Focal Point The ______ focal point of a lens is the place where parallel rays incident upon the lens ____. converge ________ Converging lens _______ Diverging lens

Focal Length

• http: //www. physics. odu. edu/hyde/Teaching/Spring 04/Lectures/318, 1, Chapter 26: Geometrical Optics