The sun is visible to us a few minutes before the actual sunrise because of :

The streaming of light beams coming from the Sun through trees is said to have suggested that light travels in straight line. The particles on the path of light beams are visible to us because

The red colour of the Sun at sunset and sunrise is due to –

A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of

The visible range of solar radiation is -

The minimum distance of clear vision for a normal healthy eye of human being is supposed to be :