Converging Lens Tutorial

1. The graphic below represents a luminous object (such as a light filament perhaps) that is placed to the left of a converging lens. The image of the object is formed at the right of the lens, and is represented by the dotted arrow. The dotted gray line represents the optic axis.

Suppose an opaque piece of cardboard is placed above the optic axis between the object and the lens as represented in the graphic below.

(a) Does the image change? If the image does change, how would it change?

 

2. The simulation applet below shows a luminous object (such as a light filament perhaps) that is placed to the left of a converging lens. The image of the object is formed at the right of the lens, and is represented by the gray arrow. The yellow horizontal line represents the optic axis. The orange lines represent three principal rays drawn from the top of the object.

(a) Approximately how many light rays are emitted from the head of the object? If the answer is infinite or zero, please say so.

(b) Approximately how many light rays are emitted from a point at the middle of the object?

(c) Approximately how many light rays are emitted from the bottom of the object?

(d) Of the rays that are emitted from each point on the object, approximately what proportion pass through the top half of the lens and approximately what proportion pass through the bottom half of the lens.

3. The simulation applet below shows the same situation as in question 2; however, at the location of the top of the object is a point light source. The point source emits light in all directions; however, only a few ray are shown.

Now, suppose a number of point sources are placed at different heights at the location of the object as shown in the simulation below. For clarity the light sources are of different colors.

Now, the object is shown superimposed with the light sources in the simulation below. The three principal rays drawn from the top of the object are shown. The object's image is represented by the gray arrow.

(a) Is it valid to consider a luminous object as being composed of an infinite number of light sources that emit light in all directions?

4. (Repeat of question 1) The graphic below represents a luminous object (such as a light filament perhaps) that is placed to the left of a converging lens. The image of the object is formed at the right of the lens, and is represented by the dotted arrow. The dotted gray line represents the optic axis.

Suppose an opaque piece of cardboard is placed above the optic axis between the object and the lens as represented in the graphic below.

(a) Does the image change? If the image does change, how would it change?