(a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it. (b) Why do stars twinkle ? Explain. OR (a) Write the function of each of the following parts of human eye : (i) Cornea (ii) Iris (iii) Crystalline lens (iv) Ciliary muscles (b) Why does the sun appear reddish early in the morning ? Will this phenomenon be observed by an astronaut on the Moon ? Give reason to justify your answer.

(a) A student is unable to see clearly the words written on the black

1.	(a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it. (b) Why do stars twinkle ? Explain. OR (a) Write the function of each of the following parts of human eye : (i) Cornea (ii) Iris (iii) Crystalline lens (iv) Ciliary muscles (b) Why does the sun appear reddish early in the morning ? Will this phenomenon be observed by an astronaut on the Moon ? Give reason to justify your answer.
Answer» (a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it. (b) Why do stars twinkle ? Explain. OR (a) Write the function of each of the following parts of human eye : (i) Cornea (ii) Iris (iii) Crystalline lens (iv) Ciliary muscles (b) Why does the sun appear reddish early in the morning ? Will this phenomenon be observed by an astronaut on the Moon ? Give reason to justify your answer.