Eye

CLASS-X

THE HUMAN EYE AND THE COLOURFUL WORLD

ASSIGNMENT-1

Q1. Name the outermost part of human eye.

Q2. Write the function of iris in the human eye.

Q3. Name the type of lens used to correct presbyopia.

Q4. When we enter a dim-lit room from a bright light, we are not able to see the object in the room for some time. Explain, why?

Q5. Why do we have two eyes instead of one eye?

Q6. A student has difficulty in reading the black board while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

Q7. What happens to the image distance in the eye when we increase the distance of an object from the eye?

Q8. A chicken can see only in the bright light. What type of cells are present in its retina?

Q9. A person is unable to see objects nearer than 50cm. He wants to read a book placed at a distance of 25cm. Find the nature, focal length and power of the lens, he requires for his spectacles.

Ans : f= +50cm , P=2D, convex lens

Q10. The near point of a hypermetropic eye is 1m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25cm.

Ans:  f= 33.3cm=0.33m

         P=+3.0D (convex lens )

Q11. A person is able to see objects clearly only when these are lying at distance between 50cm and 300cm from his eye.

i)                   What kind of defect of vision he is suffering from?

ii)                 What kind of lens will he require to increase his range of vision?

Q12. A person can see clearly only up to 3m. Prescribe a lens for spectacles so that he can see clearly up to 12m. Defect is myopia.

Ans : A concave lens of focal length 4m should be used.