To an astronaut in a spaceship, the sky appears:

1. Black                   

2. White

3. Green                 

4. Blue

For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be

(1) 5 cm

(2) 25 cm

(3) 1.67 cm

(4) 1.5 cm

A person can see objects clearly only when they lie between \(50\) cm and \(400\) cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be:

A person cannot see objects clearly that are closer than 2 m and farther than 4 m. To correct the eye vision, the person will use:

(1) Bifocal lenses of power -3.5 D and 0.25 D

(2) Bifocal lenses of power -0.25D and 3.5 D

(3) Bifocal lenses of power -0.5D and 4.0D

(4) Bifocal lenses of power -4.0D and 0.5 D

The near point of a hypermetropic eye is 1m. What is the power of the lens required to correct this defect?

(1) -3 D

(2) +3 D

(3) +1 D

(4) -1.75 D