Loading...
Propagation of Light
Quiz by GLAIZA ABUCAY
Customize this quiz to suit your class
Instantly translate to 100+ languages
Tag the questions with any skills you have. Your dashboard will track each student's mastery of each skill.
Give this quiz to my class
âWhat are the two forms in which light can exist?
âIn the wave model of light, propagation can be described when an electromagnetic wave transfer its ________, from point to another.
momentum
intensity
energy
What are the two forms in which light can exist?
In the wave model of light, propagation can be described when an electromagnetic wave transfer its ________, from point to another.
In the wave model of light, it was believed that light travels through a hypothetical substance called ________?.
In the particle model of light, to observe rectilinear propagation of light, particle light must _____________.
In the wave model of light, reflection of light waves result to __________.
According to particle model of light as proposed by Sir Isaac Newton, light is made up of particles __________ by luminous objects.
It is the bending of light when it passes through two different mediums.
Is a light a wave or a particle?
When light bounces back off an object
The only electromagnetic waves we can see
Make mcq quiz with 4 option in which one is correct -'10 Basis of Material Science ⢠.....;;;";;;"~~;;,,;;,,,,;.;.,,;;,,,;,,;.;,.,------------ 6. Temporary materials: Some materials are meant to be placed in the oral cavity for a short period of time for different reasons. ⢠Temporary crowns: While a permanent crown is prepared in the dental laboratory, the patient must wait for few days before it can be fabricated and cemented into place. Does patient experience any problems during this time period? If the tooth is vital (the pulp is alive), the patient is likely to experience pain and sensitivity while eating and drinking, also it looks unesthetic. What can be done to solve this problem? A temporary crown is placed before the patient leaves the clinic. It is constructed and luted in the same appointment in which the crown preparation is done. Temporary crowns are not very strong or esthetic but they serve adequately till the permanent crown is ready to be cemented. ⢠Temporary restorations: Sometimes it is difficult to decide immediately the best line of treatment for a particular tooth. The exact condition of the pulp may not be obvious to the dentist from the patient's symptoms. A dentist removes all or part of the decay and then places a temporary restoration to have time to observe the behaviour of the pulp or to give the pilip time to heal before deciding the further treatment required. Classification based on Location of Fabrication 4,9 Materials can be classified based on the location of fabrication into: ⢠Direct restorative materials. ⢠Indirect restorative materials Direct restorative materials: They include those materials which are used to restore cavity preparations directly in the oral cavity (Box 1.5). Box 1.5: Examples of direct restorative materials Amalgam, composites, glass ionomer and other materials, which set by chemical reactions in the mouth. Indirect restorative materials: It includes those restorations which must be fabricated outside the mouth, indirectly on a cast/ model/ die, because their processing condition would harm oral tissues. Materials used in the construction of such prosthesis are called indirect restorative materials (Box 1.6). Box 1.6: Examples of indirect restorative materials Gold inlays, crowns of metal, ceramic and polymers, which are processed at elevated temperatures. Some indirect composite restorations can be processed under specific wavelength of light, e.g. Ceramage. Classification based on Longevity of Use 1. Permanent restorations: These restorations are not planned to be replaced for a particular time period. Though they are referred to as permanent, actually they are not, e.g. fillings, crowns, bridges and dentures do not last forever (Fig. 1.5). 2. Temporary restorations: These restorations are planned to be replaced in a short period of time, such as few days to weeks. For ~ Permanent C/) c c -.2 0 c- :;::; Cll co Interim ~ Q; 0 .8ll::1iJ C/) o~ Cll a:: c:=:J Temporary Time period Fig. 1.5: Diagram depicting the time period of use of a restoration. (Arrow in permanent restoration depicts that such restorations are not planned to be replaced for a long period of time.) Introducton to Dental Materials Dental materials Box 1.7: Characteristics of metals 1. High thermal and electrical conductivity 2. Ductility (pure metals are very soft and they can be bent without breaking) 3. Opacity (they do not transmit light) 4. Luster (they have a surface that strongly reflects light and appears bright and shiny) 5. They tend to dissolve to some extent in water or other aqueous solutions, producing cations. 6. All metals are white (actually gray) except for gold, which is yellow, and copper, which is reddish. 7. All metals are solid at room temperature except mercury, which is liquid at room temperature and is used with silver alloys as amalgam. 8. All metals have high melting temperatures because of high strength of the metallic bond that holds the atoms together. 3. Polymers 4. Composites Composites are mixtures of two or more of the first three classes in which the different components remain distinct from one another in the final structure. A common example is composite resin. Fig. 1.7a: Three-dimensional structure of iron (metal) Metals Metals are the oldest of the three classes of materials that have been used as dental materials. Metals are characterized by metallic bonds (Box 1.7) which will be discussed in the next chapter. Metals solidify with their atoms in a regular or crystalline arrangement (see Chapter 2), often in the form of a cube (Fig. 1.7a). example, temporary fillings done in a tooth during root canal treatment, which have to be replaced within 2-4 days during subsequent visits. They are used to protect the tooth and provide function till the final restoration is done. 3. Interim restoration: At times, dental treatment requires "long-term" definite temporary restorations or "interim" restorations. For examle, a 7-year-old child, met with trauma and fractured one of his central incisors. A large composite build- up may serve his immediate requirement until the root formation is completed and a permanent crown is placed. 5 Classification based on the Chemical Nature of the Material These are the atoms that make up a material and the way they are bonded together determine the properties of that materiaLS Weak bonds make for weak materials and vice versa (Table 1.4). Materials can be classified into different categories based on their primary atomic bonds (Fig. 1.6): 1. Metals 2. Ceramics Fig. 1.6: Classification of dental materials based on chemical nature 12 Basis of Material Science Box 1.9: Benefits of ceramics in dentistry 1. Many ceramic oxides are used as pigmenting agents. These oxides produce good range of colors. Due to this characteristic, we are able to match almost any tooth color with good esthetic results. 2. They are inert, i.e. not chemically reactive. This quality provides ceramics with good bio- compatibility. 3. Ceramic materials are translucent, like natural teeth. This translucency gives the ceramic crown a more natural appearance than any other dental material. Fig. 1.7b: Internal arrangement of tetrahedral structure of ceramic (silica) four large oxygen atoms surround smaller silicon atom Ceramics A ceramic is a compound formed by the union of a metallic and a non-metallic element (Box 1.8). Most of these materials are oxides, formed by the union of oxygen with metals such as silicon, aluminum, calcium and magnesium (Fig.1.7b). Ceramics may be simple or complex. Examples of simple ceramics are alumina and silica. Examples of complex ceramics are feldspar (potassium aluminum silicate) and kaolin (hydrated aluminum silicate). Ceramics may be crystalline or non- crystalline (i.e. amorphous). Porcelain is a specific type of ceramic used extensively in dentistry (Box 1.9). Box 1.8: Characteristics of ceramics 1. High melting points. 2. Brittleness, which means they cannot be bent or deformed (no sliding) to any extent without actually cracking and breaking. 3. They are poor conductor of heat and electricity. 4. They are chemically inert. 5. They have excellent esthetic result in terms of matching natural teeth. Fig. 1.8: Stucture of synthetic polymer Polymers They are the latest addition (early to mid- 1900s) to dental materials. Most of the polymers are nowadays synthesized by humans. Polymers are giant, long-chain organic molecules (Fig. 1.8). Polymers are characterized by covalent bonds within each molecule, giving them tremendous strength in a single direction. Try to break a nylon rope by pulling it! They are poor conductors of heat and electri- city. Most polymers have a structure containing thousands of carbon atoms linked together like beads on a string. Others, such as silicone polymers are formed with silicon-oxygen bonds. Introducton to Dental Materials Table 1.4: Characteristics of different materials 13 Characteristics Bond Properties Crystal structure Metals Metallic bonding High strength and hardness, high electrical and thermal conductivity BCC, FCC, or HCP unit cells Ceramics Ionic or covalent bonding, or both High hardness and stiffness, electrically insulating, refractory, and chemically inert Crystalline or amorphous Polymers Covalent bonding Low sensitivity, high electrical resistivity, and low thermal conductivity, strength and stiffness vary widely Amorphous and crystalline Composites Composites are combinations of any of the basic ceramic, metallic and polymeric materials (Box 1.10). Each material that makes up composites is called a phase. Their properties tend to be somewhere between those of their basic constituents and are used to enhance their performance, longevity and handling chracterstics. Box 1.10: Types of composites in dentistry 1. Ceramic - metallic composite: Tungsten carbide bur. 2. Metal - polymer composite: Die materials in dental laboratory. 3. Ceramic - polymer composite: Enamel, dentin, bone and restorative composites. A composite is a kind of "combination" of materials, which compliment each other. The properties lacking in one material are compensated by those of the other material. For example, restorative composite has two phases, namely resin and fillers. Teeth and bones are examples of natural composites. Enamel is a composite of hydroxyapatite (which is a ceramic material) and protein (which is a polymer). EVALUATION OF DENTAL MATERIALS Most manufacturers of dental materials maintain a quality assurance programme (As per international standard like ADA specifications) and materials are thoroughly tested before being released into the market for dental practitioner (Fig. 1.9). Laboratory Evaluations Most ADA/ ANSI specifications involve laboratory tests. The tests performed as per these specifications are useful but they all are performed in vitro, (carried out in the laboratory away from the clinical conditions) which have a lot of limitations in clinical practice.lO Clinical Notes 1. For example, most of the direct restorative materials are tested for their compressive strength but ultimately the material is subjected to a combination of compressive, tensile and shear stresses, which may decide the final success or failure of the material under masticatory load. 2. Similarly upper dentures mostly fracture along the midline because of bending. Hence a bending or transverse strength ~B-a-s-is-o-f-M-a-t-e-ria-I-S~c-ie-n-c-e-------------- ---------. test is far more meaningful for denture base materials than a compression test. Clinical Trials The majority of new materials are subjected to extensive clinical trials normally in co-operation with a dental college or hospital departments prior to their release. CONCLUSION As the number of available materials is going up, it is important that the dentist remains more aware about new products so that their judgement about the selection of material remains successful. Materials which have not been thoroughly evaluated should be avoided, specially with clinical dentistry falling under Consumer Protection Act (CPA). I Research and development I iI Manufacturer/analysis Ideal requirements for clinical use: Thermal, optical, mechanical, chemical, biological Available materials and their properties are evaluated Launch of new I product Choice and selection of material by the dentist Critical assessment based on clinical performance I I H feedback to IAgricultural Tools These are commonly light tools that are being utilized in performing farm activities. They are classified as digging tools, cutting tools, cultivating tools, harvesting tools, carpentry tools, and measuring tools. Farm Implements These are commonly made of metals that serve as accessories for draft animals or mounted to machineries. They are usually used in land preparation. Farm Equipment These are machineries used in land preparation and transportation of farm inputs and products. These machineries require highly skilled operator to properly perform their respective use/sOrnamental horticulture is growing of plants for decorative and beauty purposes. â˘There many different types of flowers such as, daisies, roses and lilies. Establishment of flower beds â˘Choose the best place or site for your flower bed. â˘The site should get enough sun and have fertile soil. â˘After choosing the site, dig the area to a depth of 20- 30 cm. â˘Remove any large stones or rubbles as you dig. â˘Use a rake to level the prepared bed. This will also break up any big lumps of soil. varieties of flowers âFlame lilly âRose âMarigold âLavender star Propagation of flowers ⢠Flowers can be grown from seeds or cuttings, tubers and bulbs. From seeds From cuttings From tubers and bulbs Petunia roses Flame lilly Dahlia Elephant ear Lavender marigold Planting time ⢠Flowers can be planted all year round depending on the suitable varieties. â˘In winter they can be planted in pots, beds and greenhouses. â˘Varieties which need a lot of water should be grown during the rainy season. Management of flowers 1. weeding: ensure that the flower beds are weed free. â˘Weeds are removed by hand pulling with the help of a hand fork. 2. watering: watering should be done regularly during the dry season and less frequently during the rainy season. â˘make sure the beds are moist but avoid waterlogging. 3. fertilizing: soil should be well fertilized with super phosphate at planting. â˘Flowers should not be top dressed with ammonium nitrate as this will affect flower production. 4. pruning: use a pair of secateurs or very sharp knife to remove weak shoots and dead or diseased parts of the plant. â˘Pruning also encourages new growth and controls the height of the flowers. Harvesting â˘Cut the flowers in early bloom. â˘Allow 30cm stems, grade and remove lower leaves. â˘Tie in bundles â˘label accordingly, cure by setting 20cm of the stem in boiling water for 20 minutes. (this will make the flowers last longer) â˘Store the flowers in cool conditions Marketing ⢠Flowers need fast transport to the market. ⢠Flowers can be sold in bundles, boxes or in pots. ⢠Flowers are sold in bouquets at a local market or are packed in boxes for export market. ⢠They are bought for different occasions such as weddings, funerals and parties.PLANT PROPAGATION Plant propagation is the process of creating new plants. There are two types of propagation: sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual. Sexual propagation involves the floral parts of a plant. Asexual propagation involves taking a part of one parent plant and causing it to regenerate itself into a new plant. The resulting new plant is genetically identical to its parent. Asexual propagation involves the vegetative parts of a plant: stems, roots, or leaves. (Sorensen, 2019) ANGIOSPERMS: MONOCOTYLEDON & DICOTYLEDON The angiosperms or flowering plants are divided into two groups: monocots and dicots. Monocots have one seed leaf while dicots have two. Monocots have leaves with parallel veins while netted veins for dicots. SEED BEARING PLANTS ANGIOSPERMS & GYMNOSPERMS Seed-bearing plants could be angiosperm or flowering or gymnosperm which are non-flowering plants. The angiosperms are plants that have flowers and produce seeds enclosed within a carpel. The angiosperms are a large group and include herbaceous plants, shrubs, grasses, and most trees. Their seeds may contain one seed leaf or monocotyledon and when there are two they are dicotyledons. The gymnosperms on the other hand are seed-producing plants known as "naked seeds" like cycads, conifers, and pines. The learning materials provided below will give you comprehensive information on the difference between angiosperms and gymnosperms. SEED BEARING PLANTS The other classification of plants is what we call seed-bearing plants or vascular plants. These plants reproduce through their seeds. Most fruits and vegetables that you love to eat are seed-bearing plants. Looking at the diagram below, seed-bearing plants could be gymnosperms or non-flowering plants and angiosperms or flowering plants. The angiosperms are classified too according to the number of seed leaves: monocotyledon and dicotyledon.Physics 7A: Types of Wave Propagation & in Different MediaB. Compare and contrast two different types of logic family (TTL 7400 series and CMOS 4000 series) and provide an explanation of the meaning of the following terms used; i. Fan-out ii. Handling precautions (Static sensitive) iii. Power dissipation iv. Supply voltage v. Propagation delay TLE6AG0d-5 propagates trees and fruit-bearing trees using scientific processes: identifies the appropriate tools and equipment in plant propagation and their uses; demonstrates scientific ways of propagating fruit-bearing trees; observes healthyand safety measures in propagating fruitbearing treesPreparation of salts