Shadows form when the light is ............. by a solid object.

............. materials do not let light through.

................ materials let some light through.

................... materials let all the light through.

Which of these below affect the size of a shadow ?

Shadows change in length and position throughout the day.

When is the shortest shadow appear ?

When is the longest shadow appear ?

People told the time by ............... before they had clocks.

.................. is the amount of light in an area.

Which one is used to measure the light intensity ?

What did Isaac Newton use to explain rainbow's forming process ?