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                           Defects of vision दृष्टि दोष 1- Myopia (shortsightedness) निकट दृष्टि दोष This is the defect of vision due to which a person is not able to see distant objects clearly though they can see the nearby objects clearly.  यह दृष्टि का वह दोष है जिसमें व्यक्ति दूर की वस्तु को स्पष्ट नहीं देख सकता यद्यपि उसे पास की वस्तु स्पष्ट दिखाई देती है. 2- Hypermetropia (longsighhtedness)  दूर दृष्टि दोष This is the defect of vision due to which a person is not able to see nearby objects clearly though they can see distant objects clearly.  यह दृष्टि का वह दोष है जिसमें व्यक्ति पास की वस्तु को स्पष्ट नहीं देख सकता यद्यपि उसे दूर की वस्तु स्पष्ट दिखाई देती है. 3- Presbyopia जरा दूरदृष्टि या जरा दृष्टि दोष This is the defect of vision caused due to old age. In old age the eye loses its power of accommodation. So the eye can not accommodate to see nearby as well as distant objects or sometimes can...

                              Ray Diagram Image formation by convex mirror उत्तल दर्पण द्वारा प्रतिबिंब का बनना Important points to remember 1- The ray of light, parallel to the principal axis, after reflection from a spherical mirror, passes through focus. ( or it appears that it is coming from the focus).  2- the ray of light passing through focus ( or the rays appearing to meet at the focus), after reflection from a spherical mirror, becomes parallel to the principal axis.  3- The ray of light, passing from the centre of curvature ( or the ray of light appearing to move towards the center of curvature) after reflection from a spherical mirror, returns through the same path.  4- Real image is formed at the point where the two rays of light actually cross each other, and virtual image is formed at the point where it appears that two rays meet or the point where  it appears that the rays are e...

                                 Ray Diagram Image formation by concave mirror अवतल दर्पण द्वारा प्रतिबिंब का बनना Important points to remember 1- The ray of light, parallel to the principal axis, after reflection from a spherical mirror, passes through focus. ( or it appears that it is coming from the focus).  2- the ray of light passing through focus ( or the rays appearing to meet at the focus), after reflection from a spherical mirror, becomes parallel to the principal axis.  3- The ray of light, passing from the centre of curvature ( or the ray of light appearing to move towards the center of curvature) after reflection from a spherical mirror, returns through the same path.  4- Real image is formed at the point where the two rays of light actually cross each other, and virtual image is formed at the point where it appears that two rays meet or the point where  it appears that t...