10th
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- Sodium is always kept in kerosene. Sodium are very reactive metals and kept in kerosene oil to prevent it from coming in contact with oxygen and moisture as they react to form... 1
- Generally the ionic compounds have high melting points. Ionic compounds are mostly solids and are packed in a crystal lattice structure . They have strong electrovalent bonds between the constitue... 1
- Lemon or tamarind is used for cleaning copper vessels turned greenish. Copper reacts with carbon dioxide in the air to form copper carbonate. As a result, copper loses its shiny brown surface forming a green lay... 1
- Explain the term Gangue The impurities present in the one such as sand , rocks etc are known as gangue. 2
- Explain the term Minerals The compounds of metals that occur in nature along with the impurities are called minerals. minerals are the natural source in which the met... 1
- Explain the term Ores metals are commercially extracted from minerals at low cost and minimum efforts .These minerals are called ores. ores are raw materials for... 1
- Metallurgy Explain the terms. Metallurgy defined as extraction of metal from their pure form. metals are commercially extracted from minerals at low cost and minimum effo... 2
- Identify the pairs of metals and their ores from the following. Group A. Group B A. Bauxite. 1. Aluminium B. Cassiterite. 2.Tin c. Cinnabar. 3. Mercury 1
- Make pairs of substances and their properties Substance. Property A. Potassium bromide. 1.Combustible Substance. Property A.Potassium bromide 1. Soluble in water b. Gold. 2. High ductility. C.Sulphur. 3. Combustible. D. Neon. 4. No chemical r... 1
- Write names. a. Alloy of sodium with mercury. b. Molecular formula of the common ore of aluminum. a. Alloy of sodium with mercury. Answer:: Sodium amalgam, commonly denoted Na(Hg), is an alloy of mercury and sodium. b. Molecular formula o... 1
- An object kept 60 cm from a lens gives a virtual image 20 cm in front of the lens. Answer: focal length = −30 cm; it is a diverging (concave) lens. Using the Cartesian sign convention, the object is on the left: u = -60 cm.... 1
- Three lenses having power 2, 2.5 and 1.7 D are kept touching in a row. What is the total power of the lens combination? Answer: 6.2 D When thin lenses are kept in contact, the power of the combination is the sum of their individual powers: P = P₁ + P₂ + P₃ = 2... 1
- 5 cm high object is placed at a distance of 25 cm from a converging lens of focal length of 10 cm. Answer: the image is 16.7 cm behind the lens, 3.33 cm tall, real, inverted and diminished. Using the Cartesian sign convention: u = -25 cm,... 1
- Doctor has prescribed a lens having power +1.5 D. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision? Given: Power of lens, P = +1.5 D, f=? Now, focal length of lens, f=1/P =1/(+1.5D) =10/15 m =+0.67 m P is positive, This shows the lens is co... 1
- What is the function of iris and the muscles connected to the lens in human eye? Function of Iris: The iris is a muscular diaphragm that controls the size of the pupil, which, in turn, controls the amount of light enterin... 1
- Distinguish between b. Concave lens and Convex Lens Concave lens Convex lens It is a diverging lens because it diverges the rays falling on it. It is a converging lens because it converges the... 1
- Distinguish between: a. Farsightedness and Nearsightedness Farsightedness (hypermetropia) Nearsightedness (Myopia) In hypermetropia, person clearly sees all the far away objects, but is unable to see... 1
- Explain the working of an astronomical telescope using refraction of light. The astronomical telescope consists of two lenses: objective and eyepiece. Objective has larger focal length and diameter to accommodate max... 1
- We can not clearly see an object kept at a distance less than 25 cm from the eye. We cannot clearly see an object kept at a distance less than 25 cm from the eye. This is because when we try to see a nearby object, the eye... 1
- One can sense colours only in bright light. The retina in the eye is made of many light sensitive cells. The rod-shaped cells respond to the intensity of light while the cone-shaped ce... 1
- Simple microscope is used for watch repairs. When an object is placed within the focal length of a magnifying glass or simple microscope (convex lens), its larger and erect image is obt... 1
- At which position will you keep an object in front of a convex lens so as to get a real image of the same size as the object ? Draw a figure. When an object is placed at the centre of curvature 2F₁ of a convex lens, we will get a real image 2F₂ of the same size as the object. 1
- Draw a figure explaining various terms related to a lens Various Terms related with Lenses: 1) Optical centre : The point inside a lens on the principal axis, through which light rays pass without... 1
- Q1} Match the columns in the following table and explain them Column 1 Column 2 Column 3 Farsightedness Faraway object can be seen clearly Convex lens Presbyopia Problem of old age Bifocal lens Nearsigh... 2