Physics
Planets do not twinkle because

They are nearer to earth and hence we receive a greater amount of light.
Their distance from the earth does not change with time
They are very far away from the earth resulting in decrease in intensity of light
They emit light of a constant intensity

ANSWER DOWNLOAD EXAMIANS APP

Physics
Light houses are places with powerful lights to :

Guide and resolve traffic jams in crowded metro-cities during nights
Guide and help large crowds at religious gathering during nights
Guide and warn the ships coming from different directions in the ocean
Indicate to the incoming warships, the location of a harbour during night

ANSWER DOWNLOAD EXAMIANS APP