The sky appears blue due to
(1) reflection of light (2) refraction of light (3) total internal reflection of light (4) scattering of light
The least distance of distinct vision for a young adult with normal vision is about
(1) 25 meter (2) 2.5 cm (3) 25 cm (4) 2.5 meter
The human eye can focus object s at different distance by adjusting the focal length of the eye-lens. This is due to
(1) presbyopia (2) near-sightedness (3) accommodation (4) far-sightedness