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PHYSIC PROJECT LIGHT

PHYSIC PROJECT LIGHT. By Maria Ahmed. Contents:. What is Light ? Reflection and Refraction Mirrors and Lenses Diffraction and Interference Speed of Light Electromagnetic Spectrum Pictures.

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PHYSIC PROJECT LIGHT

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  1. PHYSIC PROJECTLIGHT By Maria Ahmed

  2. Contents: • What is Light ? • Reflection and Refraction • Mirrors and Lenses • Diffraction and Interference • Speed of Light • Electromagnetic Spectrum • Pictures

  3. Light is a form of energy just like heat and sound. It is given off as a result of atoms within a substance being given energy. The main source of light is the sun. Early people rubbed woods or stones to make light. Nowadays, we can generate light from electricity.

  4. Light have different wavelengths to have different colors. For red color, it has the longest wavelength. Light consists of photons which carry energy of light. The longer wavelength, the less photons. About Light Speed Light travels fast. In a vacuum it moves about 3 x 108 meters (186,000 miles) each second, a distance so large it’s difficult to comprehend. Here are some roughly equivalent distances: • Eight times around Earth’s equator • Most of the way from Earth to the moon

  5. SHADOW Use a light projector for an example. We can see light spread out all round on the wall. But when something blocks part of the beam. The part will show black. • It is because light is made up of millions of rays. Each individual ray travels in a straight line, when something blocked the ray, it cannot reach the screen and results in shadow

  6. REFLECTION

  7. Reflection By looking at the surface of water, we can see a clear image when the water is smooth; and a jumble of scattered image can be seen when the water is ruffled by wind. • Do you know why? Reflection is the returning, or "bouncing" of a wave off of a surface which resists that kind of wave. When it reflects, it always does so at the exact same angle it came in at.

  8. If you shine a light 45 degrees to the left, it will exit 45 degrees to the right. The angle at which the light comes in is called the angle of incidence, while the angle at which it exits is called the angle of reflection. This observation is called the scientific law of reflection, which states that the angle of incidence is equal to the angle of reflection and opposite sides of the normal – an imaginary line at right angle through the point where the rays meet.

  9. A reflection coming off a smooth surface is sharp, because the waves are allowed to return "intact", without being disturbed. But, if the reflective surface is not a smooth one, what is called diffuse reflection occurs. This is because different parts of the light hit the surface in different places at different depths and different times. This results in a mostly blurred image, which is why rough, grainy surfaces do not reflect images well.

  10. Total Internal Reflection • Total internal reflection is a special case of reflection created when when a light passes from a more optically dense medium to a less dense one at an angle such that there is no refracted ray.

  11. This how optical fibers work, the fibers are specifically constructed to produce this effect, preserving the intensity of the light as it passes through the fiber to its destination.

  12. Refraction Refraction is the change in direction of a wave when it passes into a new substance. The reason the light changes direction or "bends" is because each different substance has it's own effect on the speed of light within itself.

  13. Every substance has an optical density called the substance's index of refraction, is how well light passes through it, the higher the density, the harder time light has moving through it.

  14. Refraction and Color Separation • When light is refracted, the amount that the light bends depends on its wavelength. Light waves with short wavelengths are bent more than light waves with long wavelengths. You have already learned that white light is composed of all the colors of visible light. You also know that the different colors correspond to different wavelengths. Because of this, white light can be separated into different colors during refraction, as shown in the figure below. Color separation during refraction is partially responsible for the formation of rainbows. Rainbows are created when sunlight is refracted by water droplets.

  15. This index can be determined by taking the ratio of the speed of light in a vacuum (3x106 km/s) and the speed of light in the substance. It can also be found by taking the ratio of the sine of the angle of incidence and the angle of refraction, similar to the angles mentioned above. This equation is called Snell's Law.

  16. Where the light hits the new substance, the perpendicular to that spot is referred to as the normal. If the new substance has a higher index of refraction than the substance the light was in, the ray of light will be bent towards the normal. Conversely, if the new substance is of a lower optical density, the light will bend away from the normal.

  17. Mirrors and Lenses Mirrors and Lenses Basics Mirrors have reflective surfaces. Every mirror has a focal point, where all the light directed at that mirror converges or diverges and the distance between the mirror and that point is called the focal length.

  18. The radius of the curvature of a mirror is exactly twice the focal length. Mirrors can create both real and virtual images, real being images that are actually there, virtual images only being able to be seen by looking into the mirror. Images are also either inverted or erect, upside down or right side up respectively.

  19. The focal length is referred to as F and the radius of curvature 2F. The magnification of any mirror can be calculated by subtracting the ratio of the height of the image to the height of the object and the ratio of the distance from the mirror of the image to the distance of the object..

  20. Types of Mirrors and Lenses Plane mirrors are simple straight up mirrors. In a plane mirror, the image is always virtual and the same size but right side up as the object.

  21. A concave mirror is a converging mirror. A concave mirror bends further away in the middle than at the edges, like the inside of bowl. The image produced is dependent on the positioning of the object being viewed in the mirror. If the object is beyond 2F, the image is real, inverted, and reduced, at 2F real, inverted, the same height, between F and 2F real, inverted, and magnified, at F there is no image, and closer then F the image is virtual, erect, and magnified.

  22. A convex mirror is a diverging mirror. This is the opposite of a concave mirror, bending further away at the edges than in the middle like the outside of a bowl. Convex mirrors always produce virtual, erect, reduced images. These do suffer from spherical aberration, which is why you cant see images well one a perfectly spherical reflective surface.

  23. The image is changed by the position of the object in relation to the focal length and the radius of curvature. The images formed are similar to the concave mirrors.

  24. A concave lens is a diverging lens which works similar to the convex mirror. This lens is thicker towards the edges and thin in the middle and are used in helping correction of nearsightedness. All images produced by concave lenses are virtual, erect, and reduced.

  25. Picture This Picture shows the reflection of light from a light source. Holding a piece of crystal and letting light pass through it reflected light in different parts of the ceiling. Object is crystal ball Light reflected in circles onto the ceiling Torch is Light source

  26. Mirror Reflection This picture shows how an image is reflected from from a mirror. Virtual image by a plane mirror. Angle of reflection is equal to The angle of incidence.This Law Explains why mirrors can form images.

  27. Mirror Reflection (2) In a plane mirror, the image Is virtual, upright, the same Size as the object, and is far Behind the mirror as the Object infront. Image of Object Original Object

  28. Pencil in Glass Picture. Shows a pencil placed in a glass of water. The pencil appears to be broken or bent, due to the different index of refraction in water. Pencil appears broken

  29. Broken Pencil (2) Pencil in water appears To be bent due to refraction

  30. Broken Pencil • Another Picture to show refraction in water. Appears to Be bent

  31. Light Reflection • This picture shows the reflection of the mirror on the ceiling Reflection Mirror

  32. Experiments Done The Attached document shows the procedures carried out for doing experiments to see the concepts of Light reflection and refraction. EXPERIMENT Please see attached word document on disk.

  33. CITATION: TextBooks Giancoli, Douglas: Physics for Scientists & Engineers, Third Edition. Prentice Hall Zitzewits, Paul : Physics Principles and Problems. Merril Websites: Demonstration from Professor Brooks site: Refraction and Reflection: http://lectureonline.cl.msu.edu/%7Emmp/kap25/Snell/app.htm Physics Central Online : http://www.physicscentral.com/ American Institute of Physics: http://www.aip.org/ American Scientists: http://www.americanscientist.org/articles/99articles/Parker.html

  34. THE END

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