The Human Eye and Vision

The human eye possesses the power of accommodation. This is the power to :

• alter the diameter of the pupil as the intensity of light changes

• distinguish between lights of different colours

• focus objects at different distances

• decide which of the two objects is closer.

How does the eye change in order to focus on near or distant objects?

• The lens moves in or out

• The retina moves in or out

• The lens becomes thicker or thinner

• The pupil gets larger or smaller

Which of the following changes occur when you walk out of bright sunshine into a poorly lit room?

• The pupil becomes larger

• The lens becomes thicker

• The ciliary muscle relaxes

• The pupil becomes smaller

A person got his eyes tested. The optician’s prescription for the spectacles reads: Left eye : – 3.00 D Right eye : – 3.50 D The person is having a defect of vision called :

• presbyopia

• myopia

• astigmatism

• hypermetropia

A student sitting on the last bench in the class cannot read the writing on the blackboard clearly but he can read the book lying on his desk clearly. Which of the following statement is correct about the student?

• The near point of his eyes has receded away.

• The near point of his eyes has come closer to him.

• The far point of his eyes has receded away.

• The far point of his eyes has come closer to him.

A man driving a car can read a distant road sign clearly but finds difficulty in reading the odometer on the dashboard of the car. Which of the following statement is correct about this man?

• The near point of his eyes has receded away.

• The near point of his eyes has come closer to him.

• The far point of his eyes has receded away.

• The far point of his eyes has come closer to him.

Which of the following is not caused by the atmospheric refraction of light?

• Twinkling of stars at night

• Sun appearing higher in the sky than it actually is

• Sun becoming visible two minutes before actual sunrise

• Sun appearing red at sunset

The sky appears dark to passengers flying at very high altitudes mainly because :

• Scatterings of light is not enough at such heights.

• There is no atmosphere at great heights.

• The size of molecules is smaller than the wavelength of visible light.

• The light gets scattered towards the earth.

A near sighted person cannot see distinctly beyond 50 cm from his eye. The power in diopter of spectacle lenses which will enable him to see distant objects clearly is

• +50

• –50

• +2

• –2

The following one is not a primary colour

• Yellow

• Red

• Green

• Blue