Which one of the following phenomenon is used in optical fibres?

Which one among the following is used in a simple microscope ?

The formation of glittering colours in thin foam of soap is the result of which of the following phenomenon –

Which one of the following statement is not correct?

Rainbow is produced when sunlight falls on drops of rain. which of the following physical phenomena are responsible for this?

Which one of the following colours is seen in the middle of a Rainbow?