Give reasons:
(1) You cannot enjoy watching a movie from a very short distance from the screen in a cinema hall.
(2) A simple microscope is used by watch repairers.
(3) A concave lens is used to correct myopia.
(4) In gold age bifocal lens is necessary for some person.
(5) Concave mirrors are used in solar devices.
Give reasons:
(1) You cannot enjoy watching a movie from a very short distance from the screen in a cinema hall.
(2) A simple microscope is used by watch repairers.
(3) A concave lens is used to correct myopia.
(4) In gold age bifocal lens is necessary for some person.
(5) Concave mirrors are used in solar devices.
(1) When watching a movie from a very short distance, a blurred image is formed because if an object is too close to the eye, the lens cannot curve enough to focus the image on to the retina and this causes strain to the eyes. Therefore, we cannot enjoy watching a movie from a very short distance from the screen in a cinema hall.
(2) A magnification of about 20 times is obtained by the convex lens of small focal length used in a simple microscope. Therefore, it is used by watch repairers to see every small part of the watch clearly without causing any strain to the eyes.
(3) A myopic eye has its far point nearer than infinity. As a defect it forms the image of a distant object in front of its retina. Therefore, to correct this defect in vision, a concave lens of suitable power, which has an ability to diverge incoming rays, is used to form an image at the retina.
(4) The power of accommodation of the eye usually decreases with ageing. It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes a person may suffer from both myopia and hypermetropia. To correct this defect they require bifocal lenses which are constructed with the high power convex lens on the lower half of the frame and low power convex lens on the upper half of the frame.The high power part is used for viewing near objects, and the low power part is used for viewing far objects.
(5) Concave mirrors converge and direct the sun light inward which provides greater heat retention in solar furnaces. This allows the heating system to achieve a higher temperature. A flat or convex mirror would reflect a lot of the light outward, thus making those shapes less efficient for gathering solar heat.
(1) When watching a movie from a very short distance, a blurred image is formed because if an object is too close to the eye, the lens cannot curve enough to focus the image on to the retina and this causes strain to the eyes. Therefore, we cannot enjoy watching a movie from a very short distance from the screen in a cinema hall.
(2) A magnification of about 20 times is obtained by the convex lens of small focal length used in a simple microscope. Therefore, it is used by watch repairers to see every small part of the watch clearly without causing any strain to the eyes.
(3) A myopic eye has its far point nearer than infinity. As a defect it forms the image of a distant object in front of its retina. Therefore, to correct this defect in vision, a concave lens of suitable power, which has an ability to diverge incoming rays, is used to form an image at the retina.
(4) The power of accommodation of the eye usually decreases with ageing. It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes a person may suffer from both myopia and hypermetropia. To correct this defect they require bifocal lenses which are constructed with the high power convex lens on the lower half of the frame and low power convex lens on the upper half of the frame.The high power part is used for viewing near objects, and the low power part is used for viewing far objects.
(5) Concave mirrors converge and direct the sun light inward which provides greater heat retention in solar furnaces. This allows the heating system to achieve a higher temperature. A flat or convex mirror would reflect a lot of the light outward, thus making those shapes less efficient for gathering solar heat.
