The curved shining surface of a spoon can be considered as a

What is the reason behind the extraordinary shining of the diamond cuts in a proper way?

An astronaut sees the colour of the sky as –

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

Which type of mirror is used to see the traffic coming from behind a car ?

Which one of the following colours may be obtained by combining green and red colours ?