Explain why is the sun visible a little before actual sunrise and a little after actual sunset.

Explain why the setting sun looks red?

Explain why does an underwater object appears to be situated above its actual position.

STATE WHETHER THE FOLLOWING STATEMENTS ARE TRUE OR FALSE: The sun appears circular at sunset and sunrise, but appears flattened at noon.

Explain why friction is necessary to make the disc in Fig. 7.41 roll in the direction indicated. (a) Give the direction of frictional force at B, and the sense of frictional torque, before perfect rolling begins. (b) What is the force of friction after perfect rolling begins?

Explain why a ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path after reflection.

A cyclist has to bend a little inwards from his vertical position while turning. Why?