Physics Light and Optics - Part 1 PDF

‫‪Physics‬‬ ‫‪Light and Optics‬‬ ‫‪Part – 1‬‬ ‫ما تنسوش تتابعونا على‬ ‫تطبيق البشير‬  Light and optics Light is electromagnetic waves travels with speed of 𝐶 = 3 𝑥108 m/sec. Reflection of light...

‫‪Physics‬‬ ‫‪Light and Optics‬‬ ‫‪Part – 1‬‬ ‫ما تنسوش تتابعونا على‬ ‫تطبيق البشير‬  Light and optics Light is electromagnetic waves travels with speed of 𝐶 = 3 𝑥108 m/sec. Reflection of light from a flat mirror: It was known that when a light incident on a flat polished surface, the ray is reflected in such a way that the angle of reflection θ𝑟, is equal to the angle of incidence θ𝑖. Laws of reflection are: 1. The angle of incidence equal to the angle of reflection. 2. The incident ray, the reflected ray, and the perpendicular to the reflecting surface all lies in the same horizontal plane. Refraction of light: When light is incident on a transparent material, the light divides at the surface into two parts. One part of the light is reflected. The reminder of the light is transmitted through the material. The bending of a light as it passes from one medium to another is called refraction. When Φ < θi, we say that the optical density of the second medium is greater than that of the first medium. 𝐒𝐩𝐞𝐞𝐝 𝐨𝐟 𝐥𝐢𝐠𝐡𝐭 𝐢𝐧 𝐯𝐚𝐜𝐮𝐮𝐦 𝑪 𝑰𝒏𝒅𝒆𝒙 𝒐𝒇 𝒓𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒐𝒏 = 𝒏 = = 𝐬𝐩𝐞𝐞𝐝 𝐨𝐟 𝐥𝐢𝐠𝐡𝐭 𝐢𝐧 𝐦𝐞𝐝𝐢𝐮𝐦 𝑽 DR/ SHAMS 01002200666 Snell's law: It is an expression that relates the angle of incidence to the angle of refraction for alight ray that passes from one optical medium with refractive index 𝑛1 to another medium with refractive index 𝑛2. Internal Reflection: When the light is propagate from higher dense medium to less dense medium , and if the angle of incidence is greater than a certain angle called the critical angle 𝜃𝑐 (the refracted light ray moves parallel to the boundary that 𝜃2 = 90̊ ), the light will not transmitted.That is for all 𝜃𝑖 ≥ 𝜃𝑐, the light is entirely reflected at the interface which is known as total internal reflection. In this case, using Snell's law we have Since, 𝐒𝐢𝐧 𝟗𝟎 = 𝟏 so, DR/ SHAMS 01002200666 The formation of images by lenses and mirrors: 1. lenses: A lens is usually in the form of a circular piece or relatively thin glass whose surfaces are sections of spheres. The distance between the center of the lens and the focal point is called the focal length ( f )and is measured in cm, and th e power of the lens (F ) is given by DR/ SHAMS 01002200666  Difference between Real Image and Virtual Image Real Image Virtual Image The image is due to reflection or refraction, when the light The image produced when the light arising from an object arises from an object and converges to a certain point appears to strike a certain point The real image can be captured on screen as it is the result of It cannot be captured on a screen as it is the imaginary actual intersection of ray of light intersection of ray of light The images are inverted The images are erect Converging lens are used to produce the image Diverging lens are used to produce the image Concave mirror is used to produce the image A plane mirror or convex mirror is used to produce the image DR/ SHAMS 01002200666  Convex lens can form both real and virtual images depending upon the position of object placed in front of lens. The concave lens alone never forms a real image, regardless of where the object is located. The lens Equation: f : is the focal length of the lens, positive for converging lens and negative for diverging lens. 𝑥𝑜: is the distance from the lens to the object, always positive (for a single lens). 𝑥𝑖: is the distance from the lens to the image, positive if the image is on the side of the lens opposite the object, and negative if the image is on the same side of the lens as the object. Magnification: It is defined by the ratio of the light of the image formed by a lens to the light of object. ℎ𝑜: is the height of the object, positive when the object is above the axis. ℎ𝑖: is the height of the image, positive when the image is above the axis. Angular Magnification: The magnification of an image when observed by the eye is the angular magnification T. Is the ratio of the angle subtended at the eye by the image formed by an optical instrument to that subtended at the eye by the object when not viewed through the instrument. DR/ SHAMS 01002200666  2. The Mirrors: A spherical mirror is a mirror which has the shape of a piece cut out of a spherical surface. There are two types of spherical mirrors: concave, and convex. 𝒓 The focal length is half the radius of curvature f=𝟐 DR/ SHAMS 01002200666  Concave mirrors can produce both real and virtual images; they can be upright (if virtual) or inverted (if real); they can be behind the mirror (if virtual) or in front of the mirror (if real); they can also be enlarged, reduced, or the same size as object. In a convex mirror, the image of an object is always virtual and upright. The Mirror Equation: f : is the focal length of the mirror, positive for concave mirror and negative for convex mirror. 𝑥𝑜: is the object distance from the mirror, always positive. 𝑥𝑖: is the image distance, positive if the image is on the same side of the mirror as the object, and negative if the image is on the side opposite to the object. Magnification: DR/ SHAMS 01002200666 Example (1): A light ray is incident at angle of 25 on the surface between air and water. What angle due the refracted ray make with the perpendicular to the surface when the ray is incident from (a) the air side, (b) the water side? Knowing that the refractive index of water = 1.333. Solution (a) Light incident from air to water (b) Light incident from water to air Example (2): what is the critical angle for a water -Lucite boundary? & n (Lucite) = 1.4913 and n (Water) = 1.333. Solution The critical angle exists only for the case in which the light is incident from the medium with the greater optical density to the medium with lower optical density and this mean that DR/ SHAMS 01002200666 Example (3): An object is placed 12 cm to the left of a lens that has a focal length of 8 cm. where is the image located? Solution Inserting 𝑥𝑜 = 12 𝑐𝑚 and 𝑓 = 8 𝑐𝑚 into lens equation, we find 𝟏 𝟑−𝟐 𝟏 = = ,So the image is located at a distance 𝑥𝑖 = 24 𝑐𝑚 (Real Image) from the lens. 𝑿𝒊 𝟐𝟒 𝟐𝟒 Example (4): Suppose that the object in the preceding example is moved closer to the lens so that 𝑥𝑜 = 6 𝑐𝑚, What is the new image distance? Solution 𝟏 𝟑−𝟒 𝟏 = = , So the image is located at a distance 𝑥𝑖 = −24 𝑐𝑚 (Virtual Image) from the lens. 𝑿𝒊 𝟐𝟒 𝟐𝟒 The negative sign means that the image is on the same side of the lens as the object. Bioscience Essay (The Human Eye and Vision) The human eye is a marvelous optical instrument has the following function: 1. It can produce sharp images for a wide range of object distances. 2. It can function over an extremely wide range of intensity. 3. It can detect small differences in color. 4. It requires very little maintenance. 5. It can define the stage of movement or of the rest of the objects. DR/ SHAMS 01002200666 The structure of the Eye as Optical System: 1. The sclera, It covers everything except the cornea ‫ )القرنيه‬The sclera is the outer protective coating of tough elastic tissue). 2. At the front of the eye, the sclera leads into the cornea, which is a transparent structure that admits light into the eye, its radius of curvature is nearly 0.8 cm. 3. Behind the cornea, there is a colored portion of the eye which is called Iris‫القزحيه‬. 4. Circular opening intermediate the Iris called Pupil ‫ العين بؤبؤ‬through which the light enters the inner portion of the eye. The Pupil adjusts its size according to the intensity of the light falling on it, preventing overloading of the retinal System. 5. The crystalline lens, which is a convex lens and lies behind the Iris and its refractive index = 1.62. 6. The ciliary ‫ الهدبيه‬muscles which attached the lens with the inner shape that has a greater or smaller curvature than the relaxed lens (this action is called accommodation). 7. The aqueous humor ‫مائى خليط‬, it is a clear liquid filled the space between cornea and the lens. 8. The vitreous humor‫ الزجاجى الخليط‬. It is a jellylike substance filled the space between the lens and the retina. 9. The retina ‫ الشبكيه‬is a sensitive membrane rich in blood-vessels ‫ دمو يه أوعيه‬and nerve fibers ‫( الياف عصبية‬act as film or screen).The retina consist of a numerous number of sensitive elements or cells in the form of rods and cones. These elements convert light energy to electrical impulses ‫ نبضات‬which travel a long the nerve fibers. 10.The fovea ‫ النقرة‬or the yellow spot, it is the most sensitive part of the retina, it a small circle with a diameter of 0.025 cm lies at the intersection of the eye axis with the retina. Yellow spot contains cones which are responsible for color, whereas rods are responsible for dark and white light. 11. The optic nerve ‫ البصرى العصب‬, it is the collection of all fine fiber-nerves at the blind point. 12.The choroid ‫ املشيمى العين غالف‬surface lies between the sclera and the retina, the front part of it called the Iris DR/ SHAMS 01002200666