What kind of light is emitted by regular (not self-luminous) objects?

Mirror as an image forming device… Image – a pattern of light that provides visual representation of reality… Image - the optical counterpart of an object produced by an optical device as a lens or mirror … … a likeness of an object produced on a photographic material. In optics we distinguish between real and virtual images.

Image formation in a plane mirror. The image is always there, in a well defined position, whether you look at it or not. The image is formed behind the mirror at a distance equal to the distance from the object, and has size equal to the size of the object. It is a virtual image, since there is no light in the image location. The light only appears to come from there.

How exactly do we see (images of the) objects in a mirror? Pretty much the same way as when we are looking at the objects directly! And there are always much more rays emanating from an object than getting to our eyes. That’s how different people can see the same object/image

In the overhead view of the figure below, the image of the stone seen by observer 1 is at C. Where does observer 2 see the image – at A, at B, at C, at E, or not at all?

An image may be virtual or real, but in each case: Position of an image is defined just as well as position of the object! It does not depend whether or from where you are looking at it!

Looking into a mirror at yourself: For an unobstructed, complete view you only need a mirror, which is a half of your height. Question: What is going to happen to you image in the mirror if you walk away from it?

Mirrors are known to turn left into right, that is to make the image of your left hand look as your right hand. Why don’t they turn objects upside down?

Well, if you think about it, there are many other things the mirrors do not do…. But the question is still standing: Why left to right and not upside down? A short answer is it is because you usually hand a mirror on a wall. If you place it on the floor and sand on it, you would actually see yourself upside down.

The mirrors actually do a very special transformation, known as inversion, which cannot be reduced to translations and rotations… Maybe to turning inside out?... Chiral objects and chiral molecules…

Do you need a mirror to form an image? Not necessarily. You can do reasonably well with a flat refracting surface. The image formed by a flat refracting surface is on the same side of the surface as the object –The image is virtual –The image is formed between the object and the surface –The rays bend away from the normal since n 1 > n 2 n1n1 n2n2

Examples of using of the ray approximation: 1) A point source, a screen, and a 1D and 2D apertures between them. What is the shape of the image on the screen? Image of what is it? What does its size depend on? The shape of the image corresponds to the shape of the object or of the aperture; Its size is proportional to the size of the aperture and to the ratio of distances The image is an image of the object (aperture);

Image by an aperture and sunlight: It is always the image of the aperture corresponding to its profile. It is formed everywhere in space past the aperture (an opening, a window). The image on a screen past an aperture is going to be relatively sharp, wherever you put the screen, but it becomes less sharp as the screen is moved furtehr away from the aperture. WHY?

Examples of using the ray approximation: 1) How do you get a point source? What does it mean, rays filling the aperture? What happens if we close a half of the aperture? 2) Two point sources, an aperture and a screen. Want kind of pattern on the screen do they produce? What about a line of point sources? 3) A line of point sources and a very small (pinhole) aperture. What kind of image will be on the screen? What happens if we cover a half of the aperture?

Image of the aperture Image of the aperture.. mostly Image of both the aperture and the source. How do we get an image of the source?

Congratulations! We have just discovered the earliest model of photo camera, Camera obscura. What are the drawbacks of the camera obscura? A pinhole does not let much light through. If you make the pinhole larger, the sharpness is lost. How do we improve a pinhole?

Thin Lenses A thin lens consists of a piece of glass or plastic, ground so that each of its two refracting surfaces is a segment of either a sphere or a plane… A lens is thin when the radii of curvature are much bigger than its thickness. Lenses have two major applications: light collection and imaging Converging lenses are thickest in the middle and have positive focal lengths Diverging lenses are thickest at the edges and have negative focal lengths