|Ray Box KIT or light box KIT
A Ray box kit also known as a Light box kit is used to understand various optical properties .These optical properties are made practically visible and more erudite using a ray box/light box kit. A ray box/light box kit is a simple enclosed box (one side open) consisting of an incandescent bulb, various detachable slides, lenses, mirrors and color filters. These slides and lenses when used individually in a ray box/light box produce various optical properties which are determined by analyzing the distinct paths of light rays coming out of the ray box/light box. Some of the distinguished properties known by ray box/light box kit are mentioned below.
1. The Eye
To understand how the Eye locates images and how optical illusions take place if the direction of light changes after it leaves the source. The probable size of the object is related to the angle of light rays subtended at the eye by an object. How the eyes ability to sense the same colored objects are determined. The blind spot property which is exhibited when one eye is open is also determined through a ray box/light box kit.
2. The Plane Mirror
The properties of reflection of light from a plane mirror are examined. The study of characteristics reveals the location of the image formed by a plane mirror. The least size of mirror is calculated that will just enable the whole face to be seen as the image. This phenomenon can be cross checked with a plane mirror and a piece of a paper with a window cut in it to size.
3. Multiple Images in Plane Mirrors
Two plane mirrors are so erected that they touch at one edge. The angle between them is varied so as to make multiple images. The relationship between the number of images formed and the angle between the mirrors is examined so as to calculate a precise equation.
4. Images formed by Lenses
The real and virtual images formed by concave and convex lenses are examined with the help of lenses present in the ray box/light box kit. The optical characteristics to locate images is first made using real images formed by a convex lens and are then proved correct by projecting these images onto a screen. The position of the object is varied and the effect on the nature, position, size and orientation is analyzed. The phenomenon of parallax is then used to locate virtual images formed by convex and concave lenses.
5. Images formed by Curved Mirrors
Students use what they have learned about images formed by lenses to investigate those formed by curved mirors. Very little direction is given in this experiment as it parallels the previous one on lenses.
6. Ray Tracing
The principle rays are introduced and students draw scaled ray diagrams to predict the nature, position, size and orientation of real and virtual images formed by concave and convex lenses and mirror. Magnification is defined and this is related to the distance of the image and the object from the lens or mirror.
7. The Lens Formula
Students measure the distance of the object and its real image from a convex lens for a range of object distances. This leads to the discovery of the formula 1/u +1/v = 1/f. The formula is tested and then tested when a vitual image is formed. The real is positive sign convention is introduced and students learn to calculate the position and size of an image formed by an object near convex and concave lenses and mirrors. Calculations are checked using the apporopriate lens or mirror and using a candle as the object.
Students investigate the saving of a person at the beach and discover the path across the sand and through the water that will result in reaching the person in the smallest possible time. They discover ‘Snell’s Law’ concerning the angles they run and swim when moving along the minimum time path. Using a ray box and a semicircular plasic block they discover the same law applies to light. Refractive index is defined and determined for both plastic and water. Students learn to determine the path light will follow when it passes between any two substances. They check their calculation by putting the plastic block inside the water tank.
9. Total Internal Reflection and Dispersion
Students discover the conditions needed for TIR to occur and then calculate the critical angle for a plastic/air boundary. They check the prediction with a ray box and a plastic block. They calculate the critical angle for a plastic/water boundary and check their calculation by putting the block into a semicircular water tank. Students then investigate dispersion and determine the refractive index of the plastic block when different colours of the spectrum pass through it.
10. The Convex Lens
Students calculate and draw on a large scale diagram, the paths followed by light through a convex lens. The three ligh paths are parallel to the axis of the lens. Students measure angles of incidence and calculate angles of refraction at the air/glass and glass/air boundaries and discover the the position of the principle focus of the lens. They compare their result with the the value obtained using the Lens Makers Formula. A very valuable exercise. Student have been known to say they ‘get it better’ after completing it.
11. The Eye part
Students investigate how the eye focusses on objects They use a convex lens and a screen to model the eye and replace the lens with one of a different shape when the object is moved. The effect of pupil size and depth of field is studied. Defects of vision are is investigated and students add additional lenses to ‘defective’ model eyes to produce a sharp image on the scrreen for both long and short sighted eyes.
12. Fire in Diamonds
Students plot paths of light through a large scale diagram of a diamond with Tolkowski’s cut. They discover how to produce the fire effect – the coloured flash. A diamond ring is set up and the students look at it from the predicted direction and find the phenomenon called fire in diamonds.
13. The Rainbow
Students plot the path of light through the diagram of a large water drop. They predict the angle of exit of the light and the angle subtended at the eye by a rainbow. Students check their calculations using a plastic vial filled with water and a ray box, and viewing the rainbow formed in a water sprinkler.
14. The Magnifying Glass
In this experiment students construct a 1:2 scale diagram of a person looking at a spider through a convex lens used as a magnifying glass. The concept of angular magnification is introduced and students determine the theoretical value using the scale diagram. Using a spider on a screen, a convex lens and two set squares students check their prediction by measuring the angular magnification as seen when looking through the lens. This is repeated for a range of values, the maximum angular magnification is determined and related to the focal length of the lens.
15. The Compound Microscope
Students use two convex lenses to create a model microscope. They learn how to make the final image form at the distance of the near point. By putting a ruler at the near point they can measure the width of the image when looking into the eyepiece. The theoretical linear magnification is determined and compared with the value calculated from the measurements. The effect that the distance between the lenses has on the magnification is investigated.
Students trace rays through a diagram of a Keplerian and a Galilean telescope. The angular magnification produced is related to the focal lengths of the lenses used. The concept of the eyering is introduced. Students construct the two telescopes and view an object at the far end of the room. The angular magnifications produced by the telescopes are determined from a series of measurements and compared with the focal lengths of the lenses. The advantages and disadvantages of the Keplerian versus the Galilean type are discussed.
17. The SLR Camera
Students investigate the following aspects of an SLR camera : method of focussing, the pentaprism and the focussing screen, field of view, size of image, focal ratio of the lens, brightness of image, depth of field, exposure time and ASA of film. They learn how the ASA, focal ratio, and exposure time are interrelated and how the depth of field can be controlled with suitable combinations of the three variables.
18. Colour Filtration
Students use a computer interface and a light sensor to measure the percentage transmission of the different parts of the complete spectrum through different coloured filters and then plot graphs of percentage transmission versus colour for each filter.
19. Colour Photography
Students are introduced to the primary colours and their coresponding complimentary colours. Students then go through the process of producing a colour print from a colour negative. They are given a scene and imagine taking a picture of it. They use coloured pencils to fill in the the coloured dyes in the different colour sensitive layers on the film and the printing paper that are produced when they are developed. They colour in the negative and then colour in the print after analysing which parts of the complete spectrum pass through the different combinations of dyes. Senior students really enjoy this exercise. They learn how the colours of a scene are reproduced on a print and they do some colouring – something they haven’t done for ages! A Colour transparency file of completed diagrams included.