State the symptom cause and the nature of the lens used to correct the following defect of vision. Presbyopia.

What is myopia?What are its causes ?Name the type of the lens to correct this defect.

What is myopia? What are its causes? Name the type of the lens to correct this defect.

Which of the following is not correct for Frenkel defect in crystals?

The near point of a hypermetropia eye is 1 m find the power of the lens required to correct this defect . Assume that near point of the normal eye is 25 cm

The questions given below consist of an assertion and the reason. Use the following key to choose the appropriate answer. (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion. (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.(c) Assertion is is CORRECT but reason is INCORRECT. (d) If assertion is INCORRECT but reason is CORRECT. (e)If both assertion and reason are INCORRECT. Assertion: Frenkel and Schottky defects are stoichiometric defects REason:Both defects change the density of the crystalline solid.

The questions given below consist of an assertion and the reason. Use the following key to choose the appropriate answer. (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion. (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.(c) Assertion is is CORRECT but reason is INCORRECT. (d) If assertion is INCORRECT but reason is CORRECT. (e)If both assertion and reason are INCORRECT. Assertion: In Frenkel defect no density of hte crytalline solid does not change. Reason: In Frenkel defect no cation or anion leaves the crystal.