Doubtly
@Doubtly · Joined Feb 2021
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- Make a Power point presentation about the construction and use of binoculars. Binoculars are an important device. A PowerPoint presentation on it can be made with 3-4 slides. The first slide will talk about how binocul... 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
- The Pulley appreciation of the poem The title of the poem is ‘The Pulley’. The poem is written by Welsh poet George Herbert who was a priest by profession. Each stanza of the p... 1
- Read the poem again {Animals} and write an appreciation of the poem in a paragraph format with the help of given points. (Refer to page no. 5) The poem 'Animals' has been penned by Walt Whitman. The central idea of the poem is that animals today are better than humans. The poet has... 1
- Read the poem again and write an appreciation of the poem in a paragraph format. (Refer to page no. 5) The poem ‘All the World’s a Stage’ is by William Shakespeare. It is taken from Shakespeare’s play ‘As you like It’. It is a monologue by one... 1