What is meant by power of accommodation of the eye?
The power Of accommodation of the eye is the ability of the eye to observe the distinct objects clearly which are situated at a large distance from the eye. The ciliary muscles are responsible to change the focal length Of the eye lens. The value of the power of accommodation Of the normal human eye is (d = 25 cm) = 100/f = 100/d = 100/25 = 4 dioptres. The value of power of accommodation Of human eye is about 4D
How is the length of the telescope tube related to the distance between the objective and the eyepiece of the telescope? How can the magnification of the telescope be increased?
Give the condition required to achieve a larger magnification of a small object by a compound microscope ?
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected ?
Why does the objective lens of an astronomical telescope have a large light gathering power?
Which of the two, objective or eye-piece, of a telescope has a large aperture? Give reason for your answer.
Where should an object be placed in front of a convex lens so as to use it as a simple microscope?
A person having a myopic eye used the concave lens of focal length 50cm. What is the power of the lens?
A 52-year old near-sighted person wears eye-glass with a power of –5.5 dioptres for distance viewing. His doctor prescribes a correction of +1.5 dioptres in the near-vision section of his bi-focals. This is measured relative to the main part of the lens (i) What is the focal length of his distance-viewing part of the lens? (ii) What is the focal length of the near-vision section of the lens?
What are the common defects of vision that can be corrected by the use of suitable eyeglasses or spectacles?
Which phenomenon of vision is made use of in cinematography? Explain briefly how it is used.
When is a person said to have developed cataract in his eye? How is the vision of a person having cataract restored?
A person needs a lens of power – 4.5 D for correction of her vision.
(a) What kind of defect in vision is she suffering from?
(b) What is the focal length of the corrective lens?
(c) What is the nature of the corrective lens?
A telescope has an objective of focal length 140.0 cm and an eyepiece of focal length 5.0 cm. Find
(i) the magnification of the telescope for viewing distant objects for normal adjustment
(ii) separation between the objective lens and the eyepiece.
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye ¡s 1 m. What ¡s the power of a lens required to correct this defect? Assume that near point of the normal eye is 25 cm.
How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?